kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).

Unfortunately I can't reproduce it.

==================================================================
BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615

CPU: 1 PID: 26615 Comm: syz-executor Not tainted
4.11.0-rc1-next-20170308-xc2-dirty #3
Hardware name: Hardkernel ODROID-C2 (DT)
Call trace:
[<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
[<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
[<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
[<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
[<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
[<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
[<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
[<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
[<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
[<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
[<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
[<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
[<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
[<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
[<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
[<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
[<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
[<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
[<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
[<ffff200008083f70>] el0_svc_naked+0x24/0x28

Allocated by task 26657:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
 slab_post_alloc_hook mm/slab.h:456 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 slab_alloc mm/slub.c:2726 [inline]
 kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
 __split_vma+0x118/0x608 mm/mmap.c:2515
 do_munmap+0x194/0x9b0 mm/mmap.c:2636
Freed by task 26657:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kmem_cache_free+0x80/0x258 mm/slub.c:2983
 __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff80003b9a2000
 which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
The buggy address is located 64 bytes inside of
 184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
The buggy address belongs to the page:
page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff80005ac99980

Memory state around the buggy address:
 ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
 ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).

Unfortunately I can't reproduce it.

==================================================================
BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615

CPU: 1 PID: 26615 Comm: syz-executor Not tainted
4.11.0-rc1-next-20170308-xc2-dirty #3
Hardware name: Hardkernel ODROID-C2 (DT)
Call trace:
[<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
[<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
[<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
[<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
[<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
[<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
[<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
[<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
[<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
[<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
[<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
[<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
[<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
[<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
[<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
[<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
[<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
[<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
[<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
[<ffff200008083f70>] el0_svc_naked+0x24/0x28

Allocated by task 26657:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
 slab_post_alloc_hook mm/slab.h:456 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 slab_alloc mm/slub.c:2726 [inline]
 kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
 __split_vma+0x118/0x608 mm/mmap.c:2515
 do_munmap+0x194/0x9b0 mm/mmap.c:2636
Freed by task 26657:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kmem_cache_free+0x80/0x258 mm/slub.c:2983
 __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff80003b9a2000
 which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
The buggy address is located 64 bytes inside of
 184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
The buggy address belongs to the page:
page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff80005ac99980

Memory state around the buggy address:
 ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
 ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> Hi,
>
> I've got the following error report while fuzzing the kernel with syzkaller.
>
> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>
> Unfortunately I can't reproduce it.
>
> ==================================================================
> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>
> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
> 4.11.0-rc1-next-20170308-xc2-dirty #3
> Hardware name: Hardkernel ODROID-C2 (DT)
> Call trace:
> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>
> Allocated by task 26657:
>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>  save_stack mm/kasan/kasan.c:515 [inline]
>  set_track mm/kasan/kasan.c:527 [inline]
>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>  slab_post_alloc_hook mm/slab.h:456 [inline]
>  slab_alloc_node mm/slub.c:2718 [inline]
>  slab_alloc mm/slub.c:2726 [inline]
>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>  __split_vma+0x118/0x608 mm/mmap.c:2515
>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
> Freed by task 26657:
>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>  save_stack mm/kasan/kasan.c:515 [inline]
>  set_track mm/kasan/kasan.c:527 [inline]
>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>  slab_free_hook mm/slub.c:1357 [inline]
>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>  slab_free mm/slub.c:2961 [inline]
>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>
> The buggy address belongs to the object at ffff80003b9a2000
>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
> The buggy address is located 64 bytes inside of
>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
> The buggy address belongs to the page:
> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
> flags: 0xfffc00000000100(slab)
> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
> page dumped because: kasan: bad access detected
> page->mem_cgroup:ffff80005ac99980
>
> Memory state around the buggy address:
>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                            ^
>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

Another one that looks related and doesn't have parts of stack traces missing:

==================================================================
BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360

CPU: 2 PID: 4360 Comm: syz-executor Not tainted
4.11.0-rc1-next-20170308-xc2-dirty #3
Hardware name: Hardkernel ODROID-C2 (DT)
Call trace:
[<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
[<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
[<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
[<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
[<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
[<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
[<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
[<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
[<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
[<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
[<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
[<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
[<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
[<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
[<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
[<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
[<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
[<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
[<ffff200008083f70>] el0_svc_naked+0x24/0x28

Allocated by task 4365:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
 slab_post_alloc_hook mm/slab.h:456 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 slab_alloc mm/slub.c:2726 [inline]
 kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
 __split_vma+0x118/0x608 mm/mmap.c:2515
 do_munmap+0x194/0x9b0 mm/mmap.c:2636
 mmap_region+0x138/0xc78 mm/mmap.c:1616
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2122 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

Freed by task 4365:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kmem_cache_free+0x80/0x258 mm/slub.c:2983
 __vma_adjust+0x6b0/0xff8 mm/mmap.c:890
 vma_merge+0x880/0xa40 mm/mmap.c:1135
 mmap_region+0x1f4/0xc78 mm/mmap.c:1633
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2122 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff800031a03e88
 which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
The buggy address is located 8 bytes inside of
 184-byte region [ffff800031a03e88, ffff800031a03f40)
The buggy address belongs to the page:
page:ffff7e0000c680c0 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000100100010
raw: dead000000000100 dead000000000200 ffff80005228d000 ffff800052540000
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff800052540000

Memory state around the buggy address:
 ffff800031a03d80: fc fc 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff800031a03e00: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff800031a03e80: fc fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff800031a03f00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff800031a03f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> Hi,
>
> I've got the following error report while fuzzing the kernel with syzkaller.
>
> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>
> Unfortunately I can't reproduce it.
>
> ==================================================================
> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>
> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
> 4.11.0-rc1-next-20170308-xc2-dirty #3
> Hardware name: Hardkernel ODROID-C2 (DT)
> Call trace:
> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>
> Allocated by task 26657:
>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>  save_stack mm/kasan/kasan.c:515 [inline]
>  set_track mm/kasan/kasan.c:527 [inline]
>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>  slab_post_alloc_hook mm/slab.h:456 [inline]
>  slab_alloc_node mm/slub.c:2718 [inline]
>  slab_alloc mm/slub.c:2726 [inline]
>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>  __split_vma+0x118/0x608 mm/mmap.c:2515
>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
> Freed by task 26657:
>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>  save_stack mm/kasan/kasan.c:515 [inline]
>  set_track mm/kasan/kasan.c:527 [inline]
>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>  slab_free_hook mm/slub.c:1357 [inline]
>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>  slab_free mm/slub.c:2961 [inline]
>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>
> The buggy address belongs to the object at ffff80003b9a2000
>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
> The buggy address is located 64 bytes inside of
>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
> The buggy address belongs to the page:
> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
> flags: 0xfffc00000000100(slab)
> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
> page dumped because: kasan: bad access detected
> page->mem_cgroup:ffff80005ac99980
>
> Memory state around the buggy address:
>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                            ^
>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

Another one that looks related and doesn't have parts of stack traces missing:

==================================================================
BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360

CPU: 2 PID: 4360 Comm: syz-executor Not tainted
4.11.0-rc1-next-20170308-xc2-dirty #3
Hardware name: Hardkernel ODROID-C2 (DT)
Call trace:
[<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
[<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
[<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
[<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
[<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
[<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
[<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
[<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
[<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
[<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
[<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
[<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
[<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
[<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
[<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
[<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
[<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
[<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
[<ffff200008083f70>] el0_svc_naked+0x24/0x28

Allocated by task 4365:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
 slab_post_alloc_hook mm/slab.h:456 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 slab_alloc mm/slub.c:2726 [inline]
 kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
 __split_vma+0x118/0x608 mm/mmap.c:2515
 do_munmap+0x194/0x9b0 mm/mmap.c:2636
 mmap_region+0x138/0xc78 mm/mmap.c:1616
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2122 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

Freed by task 4365:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:515 [inline]
 set_track mm/kasan/kasan.c:527 [inline]
 kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kmem_cache_free+0x80/0x258 mm/slub.c:2983
 __vma_adjust+0x6b0/0xff8 mm/mmap.c:890
 vma_merge+0x880/0xa40 mm/mmap.c:1135
 mmap_region+0x1f4/0xc78 mm/mmap.c:1633
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2122 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff800031a03e88
 which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
The buggy address is located 8 bytes inside of
 184-byte region [ffff800031a03e88, ffff800031a03f40)
The buggy address belongs to the page:
page:ffff7e0000c680c0 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000100100010
raw: dead000000000100 dead000000000200 ffff80005228d000 ffff800052540000
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff800052540000

Memory state around the buggy address:
 ffff800031a03d80: fc fc 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff800031a03e00: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff800031a03e80: fc fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff800031a03f00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff800031a03f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Suzuki K Poulose]

On 10/03/17 15:50, Andrey Konovalov wrote:
> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>> Hi,
>>
>> I've got the following error report while fuzzing the kernel with syzkaller.
>>
>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>
>> Unfortunately I can't reproduce it.
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>
>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>> Hardware name: Hardkernel ODROID-C2 (DT)
>> Call trace:
>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>
>> Allocated by task 26657:
>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>  save_stack mm/kasan/kasan.c:515 [inline]
>>  set_track mm/kasan/kasan.c:527 [inline]
>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>  slab_alloc_node mm/slub.c:2718 [inline]
>>  slab_alloc mm/slub.c:2726 [inline]
>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>> Freed by task 26657:
>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>  save_stack mm/kasan/kasan.c:515 [inline]
>>  set_track mm/kasan/kasan.c:527 [inline]
>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>  slab_free_hook mm/slub.c:1357 [inline]
>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>  slab_free mm/slub.c:2961 [inline]
>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>
>> The buggy address belongs to the object at ffff80003b9a2000
>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>> The buggy address is located 64 bytes inside of
>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>> The buggy address belongs to the page:
>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>> flags: 0xfffc00000000100(slab)
>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>> page dumped because: kasan: bad access detected
>> page->mem_cgroup:ffff80005ac99980
>>
>> Memory state around the buggy address:
>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                                            ^
>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>
> Another one that looks related and doesn't have parts of stack traces missing:
>
> ==================================================================
> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>
> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
> 4.11.0-rc1-next-20170308-xc2-dirty #3
> Hardware name: Hardkernel ODROID-C2 (DT)
> Call trace:
> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817

It looks like we don't take the mmap_sem before calling find_vma() in
stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
the race, with probably the test trying to unmap ranges in between.

Suzuki

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Suzuki K Poulose]

On 10/03/17 15:50, Andrey Konovalov wrote:
> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>> Hi,
>>
>> I've got the following error report while fuzzing the kernel with syzkaller.
>>
>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>
>> Unfortunately I can't reproduce it.
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>
>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>> Hardware name: Hardkernel ODROID-C2 (DT)
>> Call trace:
>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>
>> Allocated by task 26657:
>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>  save_stack mm/kasan/kasan.c:515 [inline]
>>  set_track mm/kasan/kasan.c:527 [inline]
>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>  slab_alloc_node mm/slub.c:2718 [inline]
>>  slab_alloc mm/slub.c:2726 [inline]
>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>> Freed by task 26657:
>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>  save_stack mm/kasan/kasan.c:515 [inline]
>>  set_track mm/kasan/kasan.c:527 [inline]
>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>  slab_free_hook mm/slub.c:1357 [inline]
>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>  slab_free mm/slub.c:2961 [inline]
>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>
>> The buggy address belongs to the object at ffff80003b9a2000
>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>> The buggy address is located 64 bytes inside of
>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>> The buggy address belongs to the page:
>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>> flags: 0xfffc00000000100(slab)
>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>> page dumped because: kasan: bad access detected
>> page->mem_cgroup:ffff80005ac99980
>>
>> Memory state around the buggy address:
>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                                            ^
>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>
> Another one that looks related and doesn't have parts of stack traces missing:
>
> ==================================================================
> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>
> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
> 4.11.0-rc1-next-20170308-xc2-dirty #3
> Hardware name: Hardkernel ODROID-C2 (DT)
> Call trace:
> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817

It looks like we don't take the mmap_sem before calling find_vma() in
stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
the race, with probably the test trying to unmap ranges in between.

Suzuki

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Suzuki K Poulose]

On 10/03/17 15:50, Andrey Konovalov wrote:
> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>> Hi,
>>
>> I've got the following error report while fuzzing the kernel with syzkaller.
>>
>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>
>> Unfortunately I can't reproduce it.
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>
>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>> Hardware name: Hardkernel ODROID-C2 (DT)
>> Call trace:
>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>
>> Allocated by task 26657:
>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>  save_stack mm/kasan/kasan.c:515 [inline]
>>  set_track mm/kasan/kasan.c:527 [inline]
>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>  slab_alloc_node mm/slub.c:2718 [inline]
>>  slab_alloc mm/slub.c:2726 [inline]
>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>> Freed by task 26657:
>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>  save_stack mm/kasan/kasan.c:515 [inline]
>>  set_track mm/kasan/kasan.c:527 [inline]
>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>  slab_free_hook mm/slub.c:1357 [inline]
>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>  slab_free mm/slub.c:2961 [inline]
>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>
>> The buggy address belongs to the object at ffff80003b9a2000
>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>> The buggy address is located 64 bytes inside of
>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>> The buggy address belongs to the page:
>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>> flags: 0xfffc00000000100(slab)
>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>> page dumped because: kasan: bad access detected
>> page->mem_cgroup:ffff80005ac99980
>>
>> Memory state around the buggy address:
>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                                            ^
>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>
> Another one that looks related and doesn't have parts of stack traces missing:
>
> ==================================================================
> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>
> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
> 4.11.0-rc1-next-20170308-xc2-dirty #3
> Hardware name: Hardkernel ODROID-C2 (DT)
> Call trace:
> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817

It looks like we don't take the mmap_sem before calling find_vma() in
stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
the race, with probably the test trying to unmap ranges in between.

Suzuki

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 10/03/17 18:37, Suzuki K Poulose wrote:
> On 10/03/17 15:50, Andrey Konovalov wrote:
>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>> Hi,
>>>
>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>
>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>
>>> Unfortunately I can't reproduce it.
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>
>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>> Call trace:
>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>
>>> Allocated by task 26657:
>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>  slab_alloc mm/slub.c:2726 [inline]
>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>> Freed by task 26657:
>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>  slab_free mm/slub.c:2961 [inline]
>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>
>>> The buggy address belongs to the object at ffff80003b9a2000
>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>> The buggy address is located 64 bytes inside of
>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>> The buggy address belongs to the page:
>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>> flags: 0xfffc00000000100(slab)
>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>> page dumped because: kasan: bad access detected
>>> page->mem_cgroup:ffff80005ac99980
>>>
>>> Memory state around the buggy address:
>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>                                            ^
>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ==================================================================
>>
>> Another one that looks related and doesn't have parts of stack traces missing:
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>
>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>> Hardware name: Hardkernel ODROID-C2 (DT)
>> Call trace:
>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
> 
> It looks like we don't take the mmap_sem before calling find_vma() in
> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
> the race, with probably the test trying to unmap ranges in between.

That indeed seems like a possible failure mode. The annoying thing is 
that we're not exactly in a position to take mmap_sem in 
stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may 
have to hold mmap_sem while iterating over all the memslots.

How about the following (very lightly tested):

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 962616fd4ddd..2006a79d5912 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 	int idx;
 
 	idx = srcu_read_lock(&kvm->srcu);
+	down_read(&current->mm->mmap_sem);
 	spin_lock(&kvm->mmu_lock);
 
 	slots = kvm_memslots(kvm);
@@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 		stage2_unmap_memslot(kvm, memslot);
 
 	spin_unlock(&kvm->mmu_lock);
+	up_read(&current->mm->mmap_sem);
 	srcu_read_unlock(&kvm->srcu, idx);
 }
 
@@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	 *     |               memory region                |
 	 *     +--------------------------------------------+
 	 */
+	down_read(&current->mm->mmap_sem);
 	do {
 		struct vm_area_struct *vma = find_vma(current->mm, hva);
 		hva_t vm_start, vm_end;
@@ -1857,7 +1860,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	} while (hva < reg_end);
 
 	if (change == KVM_MR_FLAGS_ONLY)
-		return ret;
+		goto out;
 
 	spin_lock(&kvm->mmu_lock);
 	if (ret)
@@ -1865,6 +1868,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	else
 		stage2_flush_memslot(kvm, memslot);
 	spin_unlock(&kvm->mmu_lock);
+
+out:
+	up_read(&current->mm->mmap_sem);
 	return ret;
 }
 

I'm much more worried about the other report, as I don't really see yet 
how it happens. Coffee required.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 10/03/17 18:37, Suzuki K Poulose wrote:
> On 10/03/17 15:50, Andrey Konovalov wrote:
>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>> Hi,
>>>
>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>
>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>
>>> Unfortunately I can't reproduce it.
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>
>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>> Call trace:
>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>
>>> Allocated by task 26657:
>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>  slab_alloc mm/slub.c:2726 [inline]
>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>> Freed by task 26657:
>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>  slab_free mm/slub.c:2961 [inline]
>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>
>>> The buggy address belongs to the object at ffff80003b9a2000
>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>> The buggy address is located 64 bytes inside of
>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>> The buggy address belongs to the page:
>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>> flags: 0xfffc00000000100(slab)
>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>> page dumped because: kasan: bad access detected
>>> page->mem_cgroup:ffff80005ac99980
>>>
>>> Memory state around the buggy address:
>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>                                            ^
>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ==================================================================
>>
>> Another one that looks related and doesn't have parts of stack traces missing:
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>
>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>> Hardware name: Hardkernel ODROID-C2 (DT)
>> Call trace:
>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
> 
> It looks like we don't take the mmap_sem before calling find_vma() in
> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
> the race, with probably the test trying to unmap ranges in between.

That indeed seems like a possible failure mode. The annoying thing is 
that we're not exactly in a position to take mmap_sem in 
stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may 
have to hold mmap_sem while iterating over all the memslots.

How about the following (very lightly tested):

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 962616fd4ddd..2006a79d5912 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 	int idx;
 
 	idx = srcu_read_lock(&kvm->srcu);
+	down_read(&current->mm->mmap_sem);
 	spin_lock(&kvm->mmu_lock);
 
 	slots = kvm_memslots(kvm);
@@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 		stage2_unmap_memslot(kvm, memslot);
 
 	spin_unlock(&kvm->mmu_lock);
+	up_read(&current->mm->mmap_sem);
 	srcu_read_unlock(&kvm->srcu, idx);
 }
 
@@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	 *     |               memory region                |
 	 *     +--------------------------------------------+
 	 */
+	down_read(&current->mm->mmap_sem);
 	do {
 		struct vm_area_struct *vma = find_vma(current->mm, hva);
 		hva_t vm_start, vm_end;
@@ -1857,7 +1860,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	} while (hva < reg_end);
 
 	if (change == KVM_MR_FLAGS_ONLY)
-		return ret;
+		goto out;
 
 	spin_lock(&kvm->mmu_lock);
 	if (ret)
@@ -1865,6 +1868,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	else
 		stage2_flush_memslot(kvm, memslot);
 	spin_unlock(&kvm->mmu_lock);
+
+out:
+	up_read(&current->mm->mmap_sem);
 	return ret;
 }
 

I'm much more worried about the other report, as I don't really see yet 
how it happens. Coffee required.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 10/03/17 18:37, Suzuki K Poulose wrote:
> On 10/03/17 15:50, Andrey Konovalov wrote:
>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>> Hi,
>>>
>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>
>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>
>>> Unfortunately I can't reproduce it.
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>
>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>> Call trace:
>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>
>>> Allocated by task 26657:
>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>  slab_alloc mm/slub.c:2726 [inline]
>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>> Freed by task 26657:
>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>  slab_free mm/slub.c:2961 [inline]
>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>
>>> The buggy address belongs to the object at ffff80003b9a2000
>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>> The buggy address is located 64 bytes inside of
>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>> The buggy address belongs to the page:
>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>> flags: 0xfffc00000000100(slab)
>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>> page dumped because: kasan: bad access detected
>>> page->mem_cgroup:ffff80005ac99980
>>>
>>> Memory state around the buggy address:
>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>                                            ^
>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ==================================================================
>>
>> Another one that looks related and doesn't have parts of stack traces missing:
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>
>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>> Hardware name: Hardkernel ODROID-C2 (DT)
>> Call trace:
>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
> 
> It looks like we don't take the mmap_sem before calling find_vma() in
> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
> the race, with probably the test trying to unmap ranges in between.

That indeed seems like a possible failure mode. The annoying thing is 
that we're not exactly in a position to take mmap_sem in 
stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may 
have to hold mmap_sem while iterating over all the memslots.

How about the following (very lightly tested):

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 962616fd4ddd..2006a79d5912 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 	int idx;
 
 	idx = srcu_read_lock(&kvm->srcu);
+	down_read(&current->mm->mmap_sem);
 	spin_lock(&kvm->mmu_lock);
 
 	slots = kvm_memslots(kvm);
@@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 		stage2_unmap_memslot(kvm, memslot);
 
 	spin_unlock(&kvm->mmu_lock);
+	up_read(&current->mm->mmap_sem);
 	srcu_read_unlock(&kvm->srcu, idx);
 }
 
@@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	 *     |               memory region                |
 	 *     +--------------------------------------------+
 	 */
+	down_read(&current->mm->mmap_sem);
 	do {
 		struct vm_area_struct *vma = find_vma(current->mm, hva);
 		hva_t vm_start, vm_end;
@@ -1857,7 +1860,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	} while (hva < reg_end);
 
 	if (change == KVM_MR_FLAGS_ONLY)
-		return ret;
+		goto out;
 
 	spin_lock(&kvm->mmu_lock);
 	if (ret)
@@ -1865,6 +1868,9 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	else
 		stage2_flush_memslot(kvm, memslot);
 	spin_unlock(&kvm->mmu_lock);
+
+out:
+	up_read(&current->mm->mmap_sem);
 	return ret;
 }
 

I'm much more worried about the other report, as I don't really see yet 
how it happens. Coffee required.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Suzuki K Poulose]

On 13/03/17 09:58, Marc Zyngier wrote:
> On 10/03/17 18:37, Suzuki K Poulose wrote:
>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>> Hi,
>>>>
>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>
>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>
>>>> Unfortunately I can't reproduce it.
>>>>
>>>> ==================================================================
>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>
>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>> Call trace:
>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>
>>>> Allocated by task 26657:
>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>> Freed by task 26657:
>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>  slab_free mm/slub.c:2961 [inline]
>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>
>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>> The buggy address is located 64 bytes inside of
>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>> The buggy address belongs to the page:
>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>> flags: 0xfffc00000000100(slab)
>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>> page dumped because: kasan: bad access detected
>>>> page->mem_cgroup:ffff80005ac99980
>>>>
>>>> Memory state around the buggy address:
>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>                                            ^
>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>> ==================================================================
>>>
>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>
>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>> Call trace:
>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>
>> It looks like we don't take the mmap_sem before calling find_vma() in
>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>> the race, with probably the test trying to unmap ranges in between.
>
> That indeed seems like a possible failure mode. The annoying thing is
> that we're not exactly in a position to take mmap_sem in
> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
> have to hold mmap_sem while iterating over all the memslots.
>
> How about the following (very lightly tested):
>
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 962616fd4ddd..2006a79d5912 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>  	int idx;
>
>  	idx = srcu_read_lock(&kvm->srcu);
> +	down_read(&current->mm->mmap_sem);
>  	spin_lock(&kvm->mmu_lock);
>
>  	slots = kvm_memslots(kvm);
> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>  		stage2_unmap_memslot(kvm, memslot);
>
>  	spin_unlock(&kvm->mmu_lock);
> +	up_read(&current->mm->mmap_sem);
>  	srcu_read_unlock(&kvm->srcu, idx);
>  }
>
> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  	 *     |               memory region                |
>  	 *     +--------------------------------------------+
>  	 */
> +	down_read(&current->mm->mmap_sem);
>  	do {
>  		struct vm_area_struct *vma = find_vma(current->mm, hva);
>  		hva_t vm_start, vm_end;

I have added the following hunk :

@@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
                         pa += vm_start - vma->vm_start;
  
                         /* IO region dirty page logging not allowed */
-                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
-                               return -EINVAL;
+                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+                               ret = -EINVAL;
+                               goto out;
+                       }
  
                         ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
                                                     vm_end - vm_start,

>
> I'm much more worried about the other report, as I don't really see yet
> how it happens. Coffee required.

I have something about that one. Will soon post a patch for it.

Suzuki

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Suzuki K Poulose]

On 13/03/17 09:58, Marc Zyngier wrote:
> On 10/03/17 18:37, Suzuki K Poulose wrote:
>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>> Hi,
>>>>
>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>
>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>
>>>> Unfortunately I can't reproduce it.
>>>>
>>>> ==================================================================
>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>
>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>> Call trace:
>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>
>>>> Allocated by task 26657:
>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>> Freed by task 26657:
>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>  slab_free mm/slub.c:2961 [inline]
>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>
>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>> The buggy address is located 64 bytes inside of
>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>> The buggy address belongs to the page:
>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>> flags: 0xfffc00000000100(slab)
>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>> page dumped because: kasan: bad access detected
>>>> page->mem_cgroup:ffff80005ac99980
>>>>
>>>> Memory state around the buggy address:
>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>                                            ^
>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>> ==================================================================
>>>
>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>
>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>> Call trace:
>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>
>> It looks like we don't take the mmap_sem before calling find_vma() in
>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>> the race, with probably the test trying to unmap ranges in between.
>
> That indeed seems like a possible failure mode. The annoying thing is
> that we're not exactly in a position to take mmap_sem in
> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
> have to hold mmap_sem while iterating over all the memslots.
>
> How about the following (very lightly tested):
>
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 962616fd4ddd..2006a79d5912 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>  	int idx;
>
>  	idx = srcu_read_lock(&kvm->srcu);
> +	down_read(&current->mm->mmap_sem);
>  	spin_lock(&kvm->mmu_lock);
>
>  	slots = kvm_memslots(kvm);
> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>  		stage2_unmap_memslot(kvm, memslot);
>
>  	spin_unlock(&kvm->mmu_lock);
> +	up_read(&current->mm->mmap_sem);
>  	srcu_read_unlock(&kvm->srcu, idx);
>  }
>
> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>  	 *     |               memory region                |
>  	 *     +--------------------------------------------+
>  	 */
> +	down_read(&current->mm->mmap_sem);
>  	do {
>  		struct vm_area_struct *vma = find_vma(current->mm, hva);
>  		hva_t vm_start, vm_end;

I have added the following hunk :

@@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
                         pa += vm_start - vma->vm_start;
  
                         /* IO region dirty page logging not allowed */
-                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
-                               return -EINVAL;
+                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+                               ret = -EINVAL;
+                               goto out;
+                       }
  
                         ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
                                                     vm_end - vm_start,

>
> I'm much more worried about the other report, as I don't really see yet
> how it happens. Coffee required.

I have something about that one. Will soon post a patch for it.

Suzuki

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 14/03/17 11:03, Suzuki K Poulose wrote:
> On 13/03/17 09:58, Marc Zyngier wrote:
>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>> Hi,
>>>>>
>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>
>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>
>>>>> Unfortunately I can't reproduce it.
>>>>>
>>>>> ==================================================================
>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>
>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>> Call trace:
>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>
>>>>> Allocated by task 26657:
>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>> Freed by task 26657:
>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>
>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>> The buggy address is located 64 bytes inside of
>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>> The buggy address belongs to the page:
>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>> flags: 0xfffc00000000100(slab)
>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>> page dumped because: kasan: bad access detected
>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>
>>>>> Memory state around the buggy address:
>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>                                            ^
>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>> ==================================================================
>>>>
>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>
>>>> ==================================================================
>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>
>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>> Call trace:
>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>
>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>> the race, with probably the test trying to unmap ranges in between.
>>
>> That indeed seems like a possible failure mode. The annoying thing is
>> that we're not exactly in a position to take mmap_sem in
>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>> have to hold mmap_sem while iterating over all the memslots.
>>
>> How about the following (very lightly tested):
>>
>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>> index 962616fd4ddd..2006a79d5912 100644
>> --- a/arch/arm/kvm/mmu.c
>> +++ b/arch/arm/kvm/mmu.c
>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>  	int idx;
>>
>>  	idx = srcu_read_lock(&kvm->srcu);
>> +	down_read(&current->mm->mmap_sem);
>>  	spin_lock(&kvm->mmu_lock);
>>
>>  	slots = kvm_memslots(kvm);
>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>  		stage2_unmap_memslot(kvm, memslot);
>>
>>  	spin_unlock(&kvm->mmu_lock);
>> +	up_read(&current->mm->mmap_sem);
>>  	srcu_read_unlock(&kvm->srcu, idx);
>>  }
>>
>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>  	 *     |               memory region                |
>>  	 *     +--------------------------------------------+
>>  	 */
>> +	down_read(&current->mm->mmap_sem);
>>  	do {
>>  		struct vm_area_struct *vma = find_vma(current->mm, hva);
>>  		hva_t vm_start, vm_end;
> 
> I have added the following hunk :
> 
> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>                          pa += vm_start - vma->vm_start;
>   
>                          /* IO region dirty page logging not allowed */
> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
> -                               return -EINVAL;
> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
> +                               ret = -EINVAL;
> +                               goto out;
> +                       }
>   
>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>                                                      vm_end - vm_start,
> 

Ah, of course... Thanks for pointing that out, I'll fix it as I post a
proper patch.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 14/03/17 11:03, Suzuki K Poulose wrote:
> On 13/03/17 09:58, Marc Zyngier wrote:
>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>> Hi,
>>>>>
>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>
>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>
>>>>> Unfortunately I can't reproduce it.
>>>>>
>>>>> ==================================================================
>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>
>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>> Call trace:
>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>
>>>>> Allocated by task 26657:
>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>> Freed by task 26657:
>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>
>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>> The buggy address is located 64 bytes inside of
>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>> The buggy address belongs to the page:
>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>> flags: 0xfffc00000000100(slab)
>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>> page dumped because: kasan: bad access detected
>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>
>>>>> Memory state around the buggy address:
>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>                                            ^
>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>> ==================================================================
>>>>
>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>
>>>> ==================================================================
>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>
>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>> Call trace:
>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>
>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>> the race, with probably the test trying to unmap ranges in between.
>>
>> That indeed seems like a possible failure mode. The annoying thing is
>> that we're not exactly in a position to take mmap_sem in
>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>> have to hold mmap_sem while iterating over all the memslots.
>>
>> How about the following (very lightly tested):
>>
>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>> index 962616fd4ddd..2006a79d5912 100644
>> --- a/arch/arm/kvm/mmu.c
>> +++ b/arch/arm/kvm/mmu.c
>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>  	int idx;
>>
>>  	idx = srcu_read_lock(&kvm->srcu);
>> +	down_read(&current->mm->mmap_sem);
>>  	spin_lock(&kvm->mmu_lock);
>>
>>  	slots = kvm_memslots(kvm);
>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>  		stage2_unmap_memslot(kvm, memslot);
>>
>>  	spin_unlock(&kvm->mmu_lock);
>> +	up_read(&current->mm->mmap_sem);
>>  	srcu_read_unlock(&kvm->srcu, idx);
>>  }
>>
>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>  	 *     |               memory region                |
>>  	 *     +--------------------------------------------+
>>  	 */
>> +	down_read(&current->mm->mmap_sem);
>>  	do {
>>  		struct vm_area_struct *vma = find_vma(current->mm, hva);
>>  		hva_t vm_start, vm_end;
> 
> I have added the following hunk :
> 
> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>                          pa += vm_start - vma->vm_start;
>   
>                          /* IO region dirty page logging not allowed */
> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
> -                               return -EINVAL;
> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
> +                               ret = -EINVAL;
> +                               goto out;
> +                       }
>   
>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>                                                      vm_end - vm_start,
> 

Ah, of course... Thanks for pointing that out, I'll fix it as I post a
proper patch.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 14/03/17 11:03, Suzuki K Poulose wrote:
> On 13/03/17 09:58, Marc Zyngier wrote:
>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>> Hi,
>>>>>
>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>
>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>
>>>>> Unfortunately I can't reproduce it.
>>>>>
>>>>> ==================================================================
>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>
>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>> Call trace:
>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>
>>>>> Allocated by task 26657:
>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>> Freed by task 26657:
>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>
>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>> The buggy address is located 64 bytes inside of
>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>> The buggy address belongs to the page:
>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>> flags: 0xfffc00000000100(slab)
>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>> page dumped because: kasan: bad access detected
>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>
>>>>> Memory state around the buggy address:
>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>                                            ^
>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>> ==================================================================
>>>>
>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>
>>>> ==================================================================
>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>
>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>> Call trace:
>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>
>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>> the race, with probably the test trying to unmap ranges in between.
>>
>> That indeed seems like a possible failure mode. The annoying thing is
>> that we're not exactly in a position to take mmap_sem in
>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>> have to hold mmap_sem while iterating over all the memslots.
>>
>> How about the following (very lightly tested):
>>
>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>> index 962616fd4ddd..2006a79d5912 100644
>> --- a/arch/arm/kvm/mmu.c
>> +++ b/arch/arm/kvm/mmu.c
>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>  	int idx;
>>
>>  	idx = srcu_read_lock(&kvm->srcu);
>> +	down_read(&current->mm->mmap_sem);
>>  	spin_lock(&kvm->mmu_lock);
>>
>>  	slots = kvm_memslots(kvm);
>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>  		stage2_unmap_memslot(kvm, memslot);
>>
>>  	spin_unlock(&kvm->mmu_lock);
>> +	up_read(&current->mm->mmap_sem);
>>  	srcu_read_unlock(&kvm->srcu, idx);
>>  }
>>
>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>  	 *     |               memory region                |
>>  	 *     +--------------------------------------------+
>>  	 */
>> +	down_read(&current->mm->mmap_sem);
>>  	do {
>>  		struct vm_area_struct *vma = find_vma(current->mm, hva);
>>  		hva_t vm_start, vm_end;
> 
> I have added the following hunk :
> 
> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>                          pa += vm_start - vma->vm_start;
>   
>                          /* IO region dirty page logging not allowed */
> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
> -                               return -EINVAL;
> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
> +                               ret = -EINVAL;
> +                               goto out;
> +                       }
>   
>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>                                                      vm_end - vm_start,
> 

Ah, of course... Thanks for pointing that out, I'll fix it as I post a
proper patch.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On 14/03/17 11:03, Suzuki K Poulose wrote:
>> On 13/03/17 09:58, Marc Zyngier wrote:
>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>
>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>
>>>>>> Unfortunately I can't reproduce it.
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>
>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>> Call trace:
>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>
>>>>>> Allocated by task 26657:
>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>> Freed by task 26657:
>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>
>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>> The buggy address is located 64 bytes inside of
>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>> The buggy address belongs to the page:
>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>> flags: 0xfffc00000000100(slab)
>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>> page dumped because: kasan: bad access detected
>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>
>>>>>> Memory state around the buggy address:
>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>                                            ^
>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>> ==================================================================
>>>>>
>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>
>>>>> ==================================================================
>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>
>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>> Call trace:
>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>
>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>> the race, with probably the test trying to unmap ranges in between.
>>>
>>> That indeed seems like a possible failure mode. The annoying thing is
>>> that we're not exactly in a position to take mmap_sem in
>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>> have to hold mmap_sem while iterating over all the memslots.
>>>
>>> How about the following (very lightly tested):
>>>
>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>> index 962616fd4ddd..2006a79d5912 100644
>>> --- a/arch/arm/kvm/mmu.c
>>> +++ b/arch/arm/kvm/mmu.c
>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>      int idx;
>>>
>>>      idx = srcu_read_lock(&kvm->srcu);
>>> +    down_read(&current->mm->mmap_sem);
>>>      spin_lock(&kvm->mmu_lock);
>>>
>>>      slots = kvm_memslots(kvm);
>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>              stage2_unmap_memslot(kvm, memslot);
>>>
>>>      spin_unlock(&kvm->mmu_lock);
>>> +    up_read(&current->mm->mmap_sem);
>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>  }
>>>
>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>       *     |               memory region                |
>>>       *     +--------------------------------------------+
>>>       */
>>> +    down_read(&current->mm->mmap_sem);
>>>      do {
>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>              hva_t vm_start, vm_end;
>>
>> I have added the following hunk :
>>
>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>                          pa += vm_start - vma->vm_start;
>>
>>                          /* IO region dirty page logging not allowed */
>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>> -                               return -EINVAL;
>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>> +                               ret = -EINVAL;
>> +                               goto out;
>> +                       }
>>
>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>                                                      vm_end - vm_start,
>>
>
> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
> proper patch.
>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...

Hi,

I've got this report again on linux-next 4c3c5cd02318 (Apr 5).

It seems that it's still not fixed.

Thanks!

==================================================================
BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095

CPU: 0 PID: 23095 Comm: syz-executor Not tainted
4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4
Hardware name: Hardkernel ODROID-C2 (DT)
Call trace:
[<ffff20000808fb90>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
[<ffff20000808fff0>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
[<ffff2000088d5bb0>] __dump_stack lib/dump_stack.c:16 [inline]
[<ffff2000088d5bb0>] dump_stack+0x110/0x168 lib/dump_stack.c:52
[<ffff200008403d98>] print_address_description+0x60/0x248 mm/kasan/report.c:252
[<ffff2000084042a8>] kasan_report_error mm/kasan/report.c:351 [inline]
[<ffff2000084042a8>] kasan_report+0x218/0x300 mm/kasan/report.c:408
[<ffff200008404408>] __asan_report_load8_noabort+0x18/0x20 mm/kasan/report.c:429
[<ffff20000837444c>] vmacache_update+0x114/0x118 mm/vmacache.c:63
[<ffff2000083991f0>] find_vma+0xf8/0x150 mm/mmap.c:2124
[<ffff2000080dc59c>] kvm_arch_prepare_memory_region+0x2ac/0x488
arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1812
[<ffff2000080c2c18>] __kvm_set_memory_region+0x4a0/0x1340
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1029
[<ffff2000080c3af0>] kvm_set_memory_region+0x38/0x58
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1078
[<ffff2000080c7784>] kvm_vm_ioctl_set_memory_region
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1090 [inline]
[<ffff2000080c7784>] kvm_vm_ioctl+0xb94/0x1308
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2963
[<ffff20000847e590>] vfs_ioctl fs/ioctl.c:45 [inline]
[<ffff20000847e590>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
[<ffff20000847f4d0>] SYSC_ioctl fs/ioctl.c:700 [inline]
[<ffff20000847f4d0>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
[<ffff200008083f70>] el0_svc_naked+0x24/0x28

Allocated by task 23107:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:513 [inline]
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:617
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:555
 slab_post_alloc_hook mm/slab.h:457 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 slab_alloc mm/slub.c:2726 [inline]
 kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
 __split_vma+0x118/0x608 mm/mmap.c:2515
 do_munmap+0x194/0x9b0 mm/mmap.c:2636
 mmap_region+0x138/0xc60 mm/mmap.c:1616
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2149 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

Freed by task 23107:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:513 [inline]
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:590
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kmem_cache_free+0x80/0x260 mm/slub.c:2983
 __vma_adjust+0x6b0/0xff8 mm/mmap.c:890
 vma_merge+0x880/0xa40 mm/mmap.c:1135
 mmap_region+0x1f4/0xc60 mm/mmap.c:1633
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2149 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff80004d53aaa8
 which belongs to the cache vm_area_struct(673:session-6.scope) of size 184
The buggy address is located 64 bytes inside of
 184-byte region [ffff80004d53aaa8, ffff80004d53ab60)
The buggy address belongs to the page:
page:ffff7e0001354e80 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000100100010
raw: dead000000000100 dead000000000200 ffff800048440200 ffff800056825500
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff800056825500

Memory state around the buggy address:
 ffff80004d53a980: fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb
 ffff80004d53aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
>ffff80004d53aa80: fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff80004d53ab00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff80004d53ab80: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On 14/03/17 11:03, Suzuki K Poulose wrote:
>> On 13/03/17 09:58, Marc Zyngier wrote:
>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>
>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>
>>>>>> Unfortunately I can't reproduce it.
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>
>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>> Call trace:
>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>
>>>>>> Allocated by task 26657:
>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>> Freed by task 26657:
>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>
>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>> The buggy address is located 64 bytes inside of
>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>> The buggy address belongs to the page:
>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>> flags: 0xfffc00000000100(slab)
>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>> page dumped because: kasan: bad access detected
>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>
>>>>>> Memory state around the buggy address:
>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>                                            ^
>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>> ==================================================================
>>>>>
>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>
>>>>> ==================================================================
>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>
>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>> Call trace:
>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>
>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>> the race, with probably the test trying to unmap ranges in between.
>>>
>>> That indeed seems like a possible failure mode. The annoying thing is
>>> that we're not exactly in a position to take mmap_sem in
>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>> have to hold mmap_sem while iterating over all the memslots.
>>>
>>> How about the following (very lightly tested):
>>>
>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>> index 962616fd4ddd..2006a79d5912 100644
>>> --- a/arch/arm/kvm/mmu.c
>>> +++ b/arch/arm/kvm/mmu.c
>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>      int idx;
>>>
>>>      idx = srcu_read_lock(&kvm->srcu);
>>> +    down_read(&current->mm->mmap_sem);
>>>      spin_lock(&kvm->mmu_lock);
>>>
>>>      slots = kvm_memslots(kvm);
>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>              stage2_unmap_memslot(kvm, memslot);
>>>
>>>      spin_unlock(&kvm->mmu_lock);
>>> +    up_read(&current->mm->mmap_sem);
>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>  }
>>>
>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>       *     |               memory region                |
>>>       *     +--------------------------------------------+
>>>       */
>>> +    down_read(&current->mm->mmap_sem);
>>>      do {
>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>              hva_t vm_start, vm_end;
>>
>> I have added the following hunk :
>>
>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>                          pa += vm_start - vma->vm_start;
>>
>>                          /* IO region dirty page logging not allowed */
>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>> -                               return -EINVAL;
>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>> +                               ret = -EINVAL;
>> +                               goto out;
>> +                       }
>>
>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>                                                      vm_end - vm_start,
>>
>
> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
> proper patch.
>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...

Hi,

I've got this report again on linux-next 4c3c5cd02318 (Apr 5).

It seems that it's still not fixed.

Thanks!

==================================================================
BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095

CPU: 0 PID: 23095 Comm: syz-executor Not tainted
4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4
Hardware name: Hardkernel ODROID-C2 (DT)
Call trace:
[<ffff20000808fb90>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
[<ffff20000808fff0>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
[<ffff2000088d5bb0>] __dump_stack lib/dump_stack.c:16 [inline]
[<ffff2000088d5bb0>] dump_stack+0x110/0x168 lib/dump_stack.c:52
[<ffff200008403d98>] print_address_description+0x60/0x248 mm/kasan/report.c:252
[<ffff2000084042a8>] kasan_report_error mm/kasan/report.c:351 [inline]
[<ffff2000084042a8>] kasan_report+0x218/0x300 mm/kasan/report.c:408
[<ffff200008404408>] __asan_report_load8_noabort+0x18/0x20 mm/kasan/report.c:429
[<ffff20000837444c>] vmacache_update+0x114/0x118 mm/vmacache.c:63
[<ffff2000083991f0>] find_vma+0xf8/0x150 mm/mmap.c:2124
[<ffff2000080dc59c>] kvm_arch_prepare_memory_region+0x2ac/0x488
arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1812
[<ffff2000080c2c18>] __kvm_set_memory_region+0x4a0/0x1340
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1029
[<ffff2000080c3af0>] kvm_set_memory_region+0x38/0x58
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1078
[<ffff2000080c7784>] kvm_vm_ioctl_set_memory_region
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1090 [inline]
[<ffff2000080c7784>] kvm_vm_ioctl+0xb94/0x1308
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2963
[<ffff20000847e590>] vfs_ioctl fs/ioctl.c:45 [inline]
[<ffff20000847e590>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
[<ffff20000847f4d0>] SYSC_ioctl fs/ioctl.c:700 [inline]
[<ffff20000847f4d0>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
[<ffff200008083f70>] el0_svc_naked+0x24/0x28

Allocated by task 23107:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:513 [inline]
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:617
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:555
 slab_post_alloc_hook mm/slab.h:457 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 slab_alloc mm/slub.c:2726 [inline]
 kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
 __split_vma+0x118/0x608 mm/mmap.c:2515
 do_munmap+0x194/0x9b0 mm/mmap.c:2636
 mmap_region+0x138/0xc60 mm/mmap.c:1616
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2149 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

Freed by task 23107:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:513 [inline]
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:590
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kmem_cache_free+0x80/0x260 mm/slub.c:2983
 __vma_adjust+0x6b0/0xff8 mm/mmap.c:890
 vma_merge+0x880/0xa40 mm/mmap.c:1135
 mmap_region+0x1f4/0xc60 mm/mmap.c:1633
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2149 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff80004d53aaa8
 which belongs to the cache vm_area_struct(673:session-6.scope) of size 184
The buggy address is located 64 bytes inside of
 184-byte region [ffff80004d53aaa8, ffff80004d53ab60)
The buggy address belongs to the page:
page:ffff7e0001354e80 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000100100010
raw: dead000000000100 dead000000000200 ffff800048440200 ffff800056825500
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff800056825500

Memory state around the buggy address:
 ffff80004d53a980: fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb
 ffff80004d53aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
>ffff80004d53aa80: fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff80004d53ab00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff80004d53ab80: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On 14/03/17 11:03, Suzuki K Poulose wrote:
>> On 13/03/17 09:58, Marc Zyngier wrote:
>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>
>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>
>>>>>> Unfortunately I can't reproduce it.
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>
>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>> Call trace:
>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>
>>>>>> Allocated by task 26657:
>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>> Freed by task 26657:
>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>
>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>> The buggy address is located 64 bytes inside of
>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>> The buggy address belongs to the page:
>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>> flags: 0xfffc00000000100(slab)
>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>> page dumped because: kasan: bad access detected
>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>
>>>>>> Memory state around the buggy address:
>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>                                            ^
>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>> ==================================================================
>>>>>
>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>
>>>>> ==================================================================
>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>
>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>> Call trace:
>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>
>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>> the race, with probably the test trying to unmap ranges in between.
>>>
>>> That indeed seems like a possible failure mode. The annoying thing is
>>> that we're not exactly in a position to take mmap_sem in
>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>> have to hold mmap_sem while iterating over all the memslots.
>>>
>>> How about the following (very lightly tested):
>>>
>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>> index 962616fd4ddd..2006a79d5912 100644
>>> --- a/arch/arm/kvm/mmu.c
>>> +++ b/arch/arm/kvm/mmu.c
>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>      int idx;
>>>
>>>      idx = srcu_read_lock(&kvm->srcu);
>>> +    down_read(&current->mm->mmap_sem);
>>>      spin_lock(&kvm->mmu_lock);
>>>
>>>      slots = kvm_memslots(kvm);
>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>              stage2_unmap_memslot(kvm, memslot);
>>>
>>>      spin_unlock(&kvm->mmu_lock);
>>> +    up_read(&current->mm->mmap_sem);
>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>  }
>>>
>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>       *     |               memory region                |
>>>       *     +--------------------------------------------+
>>>       */
>>> +    down_read(&current->mm->mmap_sem);
>>>      do {
>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>              hva_t vm_start, vm_end;
>>
>> I have added the following hunk :
>>
>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>                          pa += vm_start - vma->vm_start;
>>
>>                          /* IO region dirty page logging not allowed */
>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>> -                               return -EINVAL;
>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>> +                               ret = -EINVAL;
>> +                               goto out;
>> +                       }
>>
>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>                                                      vm_end - vm_start,
>>
>
> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
> proper patch.
>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...

Hi,

I've got this report again on linux-next 4c3c5cd02318 (Apr 5).

It seems that it's still not fixed.

Thanks!

==================================================================
BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095

CPU: 0 PID: 23095 Comm: syz-executor Not tainted
4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4
Hardware name: Hardkernel ODROID-C2 (DT)
Call trace:
[<ffff20000808fb90>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
[<ffff20000808fff0>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
[<ffff2000088d5bb0>] __dump_stack lib/dump_stack.c:16 [inline]
[<ffff2000088d5bb0>] dump_stack+0x110/0x168 lib/dump_stack.c:52
[<ffff200008403d98>] print_address_description+0x60/0x248 mm/kasan/report.c:252
[<ffff2000084042a8>] kasan_report_error mm/kasan/report.c:351 [inline]
[<ffff2000084042a8>] kasan_report+0x218/0x300 mm/kasan/report.c:408
[<ffff200008404408>] __asan_report_load8_noabort+0x18/0x20 mm/kasan/report.c:429
[<ffff20000837444c>] vmacache_update+0x114/0x118 mm/vmacache.c:63
[<ffff2000083991f0>] find_vma+0xf8/0x150 mm/mmap.c:2124
[<ffff2000080dc59c>] kvm_arch_prepare_memory_region+0x2ac/0x488
arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1812
[<ffff2000080c2c18>] __kvm_set_memory_region+0x4a0/0x1340
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1029
[<ffff2000080c3af0>] kvm_set_memory_region+0x38/0x58
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1078
[<ffff2000080c7784>] kvm_vm_ioctl_set_memory_region
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1090 [inline]
[<ffff2000080c7784>] kvm_vm_ioctl+0xb94/0x1308
arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2963
[<ffff20000847e590>] vfs_ioctl fs/ioctl.c:45 [inline]
[<ffff20000847e590>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
[<ffff20000847f4d0>] SYSC_ioctl fs/ioctl.c:700 [inline]
[<ffff20000847f4d0>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
[<ffff200008083f70>] el0_svc_naked+0x24/0x28

Allocated by task 23107:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:513 [inline]
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:617
 kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:555
 slab_post_alloc_hook mm/slab.h:457 [inline]
 slab_alloc_node mm/slub.c:2718 [inline]
 slab_alloc mm/slub.c:2726 [inline]
 kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
 __split_vma+0x118/0x608 mm/mmap.c:2515
 do_munmap+0x194/0x9b0 mm/mmap.c:2636
 mmap_region+0x138/0xc60 mm/mmap.c:1616
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2149 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

Freed by task 23107:
 save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
 save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
 save_stack mm/kasan/kasan.c:513 [inline]
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:590
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kmem_cache_free+0x80/0x260 mm/slub.c:2983
 __vma_adjust+0x6b0/0xff8 mm/mmap.c:890
 vma_merge+0x880/0xa40 mm/mmap.c:1135
 mmap_region+0x1f4/0xc60 mm/mmap.c:1633
 do_mmap+0x3cc/0x848 mm/mmap.c:1453
 do_mmap_pgoff include/linux/mm.h:2149 [inline]
 vm_mmap_pgoff+0xec/0x120 mm/util.c:309
 SYSC_mmap_pgoff mm/mmap.c:1503 [inline]
 SyS_mmap_pgoff+0x220/0x420 mm/mmap.c:1461
 sys_mmap+0x58/0x80 arch/arm64/kernel/sys.c:37
 el0_svc_naked+0x24/0x28

The buggy address belongs to the object at ffff80004d53aaa8
 which belongs to the cache vm_area_struct(673:session-6.scope) of size 184
The buggy address is located 64 bytes inside of
 184-byte region [ffff80004d53aaa8, ffff80004d53ab60)
The buggy address belongs to the page:
page:ffff7e0001354e80 count:1 mapcount:0 mapping:          (null) index:0x0
flags: 0xfffc00000000100(slab)
raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000100100010
raw: dead000000000100 dead000000000200 ffff800048440200 ffff800056825500
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff800056825500

Memory state around the buggy address:
 ffff80004d53a980: fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb
 ffff80004d53aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
>ffff80004d53aa80: fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff80004d53ab00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff80004d53ab80: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 11/04/17 16:26, Andrey Konovalov wrote:
> On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
>> On 14/03/17 11:03, Suzuki K Poulose wrote:
>>> On 13/03/17 09:58, Marc Zyngier wrote:
>>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>>
>>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>>
>>>>>>> Unfortunately I can't reproduce it.
>>>>>>>
>>>>>>> ==================================================================
>>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>>
>>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>> Call trace:
>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>>
>>>>>>> Allocated by task 26657:
>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>>> Freed by task 26657:
>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>>
>>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>>> The buggy address is located 64 bytes inside of
>>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>>> The buggy address belongs to the page:
>>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>>> flags: 0xfffc00000000100(slab)
>>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>>> page dumped because: kasan: bad access detected
>>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>>
>>>>>>> Memory state around the buggy address:
>>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>                                            ^
>>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>> ==================================================================
>>>>>>
>>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>>
>>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>> Call trace:
>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>
>>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>>> the race, with probably the test trying to unmap ranges in between.
>>>>
>>>> That indeed seems like a possible failure mode. The annoying thing is
>>>> that we're not exactly in a position to take mmap_sem in
>>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>>> have to hold mmap_sem while iterating over all the memslots.
>>>>
>>>> How about the following (very lightly tested):
>>>>
>>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>>> index 962616fd4ddd..2006a79d5912 100644
>>>> --- a/arch/arm/kvm/mmu.c
>>>> +++ b/arch/arm/kvm/mmu.c
>>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>      int idx;
>>>>
>>>>      idx = srcu_read_lock(&kvm->srcu);
>>>> +    down_read(&current->mm->mmap_sem);
>>>>      spin_lock(&kvm->mmu_lock);
>>>>
>>>>      slots = kvm_memslots(kvm);
>>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>              stage2_unmap_memslot(kvm, memslot);
>>>>
>>>>      spin_unlock(&kvm->mmu_lock);
>>>> +    up_read(&current->mm->mmap_sem);
>>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>>  }
>>>>
>>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>       *     |               memory region                |
>>>>       *     +--------------------------------------------+
>>>>       */
>>>> +    down_read(&current->mm->mmap_sem);
>>>>      do {
>>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>>              hva_t vm_start, vm_end;
>>>
>>> I have added the following hunk :
>>>
>>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>                          pa += vm_start - vma->vm_start;
>>>
>>>                          /* IO region dirty page logging not allowed */
>>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>>> -                               return -EINVAL;
>>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>>> +                               ret = -EINVAL;
>>> +                               goto out;
>>> +                       }
>>>
>>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>>                                                      vm_end - vm_start,
>>>
>>
>> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
>> proper patch.
>>
>> Thanks,
>>
>>         M.
>> --
>> Jazz is not dead. It just smells funny...
> 
> Hi,
> 
> I've got this report again on linux-next 4c3c5cd02318 (Apr 5).
> 
> It seems that it's still not fixed.
> 
> Thanks!
> 
> ==================================================================
> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
> Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095
> 
> CPU: 0 PID: 23095 Comm: syz-executor Not tainted
> 4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4

The fixes went into -rc6. Can you please give it a go?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Marc Zyngier]

On 11/04/17 16:26, Andrey Konovalov wrote:
> On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
>> On 14/03/17 11:03, Suzuki K Poulose wrote:
>>> On 13/03/17 09:58, Marc Zyngier wrote:
>>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>>
>>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>>
>>>>>>> Unfortunately I can't reproduce it.
>>>>>>>
>>>>>>> ==================================================================
>>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>>
>>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>> Call trace:
>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>>
>>>>>>> Allocated by task 26657:
>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>>> Freed by task 26657:
>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>>
>>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>>> The buggy address is located 64 bytes inside of
>>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>>> The buggy address belongs to the page:
>>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>>> flags: 0xfffc00000000100(slab)
>>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>>> page dumped because: kasan: bad access detected
>>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>>
>>>>>>> Memory state around the buggy address:
>>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>                                            ^
>>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>> ==================================================================
>>>>>>
>>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>>
>>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>> Call trace:
>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>
>>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>>> the race, with probably the test trying to unmap ranges in between.
>>>>
>>>> That indeed seems like a possible failure mode. The annoying thing is
>>>> that we're not exactly in a position to take mmap_sem in
>>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>>> have to hold mmap_sem while iterating over all the memslots.
>>>>
>>>> How about the following (very lightly tested):
>>>>
>>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>>> index 962616fd4ddd..2006a79d5912 100644
>>>> --- a/arch/arm/kvm/mmu.c
>>>> +++ b/arch/arm/kvm/mmu.c
>>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>      int idx;
>>>>
>>>>      idx = srcu_read_lock(&kvm->srcu);
>>>> +    down_read(&current->mm->mmap_sem);
>>>>      spin_lock(&kvm->mmu_lock);
>>>>
>>>>      slots = kvm_memslots(kvm);
>>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>              stage2_unmap_memslot(kvm, memslot);
>>>>
>>>>      spin_unlock(&kvm->mmu_lock);
>>>> +    up_read(&current->mm->mmap_sem);
>>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>>  }
>>>>
>>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>       *     |               memory region                |
>>>>       *     +--------------------------------------------+
>>>>       */
>>>> +    down_read(&current->mm->mmap_sem);
>>>>      do {
>>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>>              hva_t vm_start, vm_end;
>>>
>>> I have added the following hunk :
>>>
>>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>                          pa += vm_start - vma->vm_start;
>>>
>>>                          /* IO region dirty page logging not allowed */
>>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>>> -                               return -EINVAL;
>>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>>> +                               ret = -EINVAL;
>>> +                               goto out;
>>> +                       }
>>>
>>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>>                                                      vm_end - vm_start,
>>>
>>
>> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
>> proper patch.
>>
>> Thanks,
>>
>>         M.
>> --
>> Jazz is not dead. It just smells funny...
> 
> Hi,
> 
> I've got this report again on linux-next 4c3c5cd02318 (Apr 5).
> 
> It seems that it's still not fixed.
> 
> Thanks!
> 
> ==================================================================
> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
> Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095
> 
> CPU: 0 PID: 23095 Comm: syz-executor Not tainted
> 4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4

The fixes went into -rc6. Can you please give it a go?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Tue, Apr 11, 2017 at 5:36 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On 11/04/17 16:26, Andrey Konovalov wrote:
>> On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
>>> On 14/03/17 11:03, Suzuki K Poulose wrote:
>>>> On 13/03/17 09:58, Marc Zyngier wrote:
>>>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>>>
>>>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>>>
>>>>>>>> Unfortunately I can't reproduce it.
>>>>>>>>
>>>>>>>> ==================================================================
>>>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>>>
>>>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>>> Call trace:
>>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>>>
>>>>>>>> Allocated by task 26657:
>>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>>>> Freed by task 26657:
>>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>>>
>>>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>>>> The buggy address is located 64 bytes inside of
>>>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>>>> The buggy address belongs to the page:
>>>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>>>> flags: 0xfffc00000000100(slab)
>>>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>>>> page dumped because: kasan: bad access detected
>>>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>>>
>>>>>>>> Memory state around the buggy address:
>>>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>>                                            ^
>>>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>> ==================================================================
>>>>>>>
>>>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>>>
>>>>>>> ==================================================================
>>>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>>>
>>>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>> Call trace:
>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>
>>>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>>>> the race, with probably the test trying to unmap ranges in between.
>>>>>
>>>>> That indeed seems like a possible failure mode. The annoying thing is
>>>>> that we're not exactly in a position to take mmap_sem in
>>>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>>>> have to hold mmap_sem while iterating over all the memslots.
>>>>>
>>>>> How about the following (very lightly tested):
>>>>>
>>>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>>>> index 962616fd4ddd..2006a79d5912 100644
>>>>> --- a/arch/arm/kvm/mmu.c
>>>>> +++ b/arch/arm/kvm/mmu.c
>>>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>>      int idx;
>>>>>
>>>>>      idx = srcu_read_lock(&kvm->srcu);
>>>>> +    down_read(&current->mm->mmap_sem);
>>>>>      spin_lock(&kvm->mmu_lock);
>>>>>
>>>>>      slots = kvm_memslots(kvm);
>>>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>>              stage2_unmap_memslot(kvm, memslot);
>>>>>
>>>>>      spin_unlock(&kvm->mmu_lock);
>>>>> +    up_read(&current->mm->mmap_sem);
>>>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>>>  }
>>>>>
>>>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>>       *     |               memory region                |
>>>>>       *     +--------------------------------------------+
>>>>>       */
>>>>> +    down_read(&current->mm->mmap_sem);
>>>>>      do {
>>>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>>>              hva_t vm_start, vm_end;
>>>>
>>>> I have added the following hunk :
>>>>
>>>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>                          pa += vm_start - vma->vm_start;
>>>>
>>>>                          /* IO region dirty page logging not allowed */
>>>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>>>> -                               return -EINVAL;
>>>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>>>> +                               ret = -EINVAL;
>>>> +                               goto out;
>>>> +                       }
>>>>
>>>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>>>                                                      vm_end - vm_start,
>>>>
>>>
>>> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
>>> proper patch.
>>>
>>> Thanks,
>>>
>>>         M.
>>> --
>>> Jazz is not dead. It just smells funny...
>>
>> Hi,
>>
>> I've got this report again on linux-next 4c3c5cd02318 (Apr 5).
>>
>> It seems that it's still not fixed.
>>
>> Thanks!
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>> Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095
>>
>> CPU: 0 PID: 23095 Comm: syz-executor Not tainted
>> 4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4
>
> The fixes went into -rc6. Can you please give it a go?

Ah, OK, I assumed they were in the linux-next revision I used.

Thanks!

>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

Re: kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Tue, Apr 11, 2017 at 5:36 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On 11/04/17 16:26, Andrey Konovalov wrote:
>> On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
>>> On 14/03/17 11:03, Suzuki K Poulose wrote:
>>>> On 13/03/17 09:58, Marc Zyngier wrote:
>>>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>>>
>>>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>>>
>>>>>>>> Unfortunately I can't reproduce it.
>>>>>>>>
>>>>>>>> ==================================================================
>>>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>>>
>>>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>>> Call trace:
>>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>>>
>>>>>>>> Allocated by task 26657:
>>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>>>> Freed by task 26657:
>>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>>>
>>>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>>>> The buggy address is located 64 bytes inside of
>>>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>>>> The buggy address belongs to the page:
>>>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>>>> flags: 0xfffc00000000100(slab)
>>>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>>>> page dumped because: kasan: bad access detected
>>>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>>>
>>>>>>>> Memory state around the buggy address:
>>>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>>                                            ^
>>>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>> ==================================================================
>>>>>>>
>>>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>>>
>>>>>>> ==================================================================
>>>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>>>
>>>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>> Call trace:
>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>
>>>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>>>> the race, with probably the test trying to unmap ranges in between.
>>>>>
>>>>> That indeed seems like a possible failure mode. The annoying thing is
>>>>> that we're not exactly in a position to take mmap_sem in
>>>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>>>> have to hold mmap_sem while iterating over all the memslots.
>>>>>
>>>>> How about the following (very lightly tested):
>>>>>
>>>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>>>> index 962616fd4ddd..2006a79d5912 100644
>>>>> --- a/arch/arm/kvm/mmu.c
>>>>> +++ b/arch/arm/kvm/mmu.c
>>>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>>      int idx;
>>>>>
>>>>>      idx = srcu_read_lock(&kvm->srcu);
>>>>> +    down_read(&current->mm->mmap_sem);
>>>>>      spin_lock(&kvm->mmu_lock);
>>>>>
>>>>>      slots = kvm_memslots(kvm);
>>>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>>              stage2_unmap_memslot(kvm, memslot);
>>>>>
>>>>>      spin_unlock(&kvm->mmu_lock);
>>>>> +    up_read(&current->mm->mmap_sem);
>>>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>>>  }
>>>>>
>>>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>>       *     |               memory region                |
>>>>>       *     +--------------------------------------------+
>>>>>       */
>>>>> +    down_read(&current->mm->mmap_sem);
>>>>>      do {
>>>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>>>              hva_t vm_start, vm_end;
>>>>
>>>> I have added the following hunk :
>>>>
>>>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>                          pa += vm_start - vma->vm_start;
>>>>
>>>>                          /* IO region dirty page logging not allowed */
>>>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>>>> -                               return -EINVAL;
>>>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>>>> +                               ret = -EINVAL;
>>>> +                               goto out;
>>>> +                       }
>>>>
>>>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>>>                                                      vm_end - vm_start,
>>>>
>>>
>>> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
>>> proper patch.
>>>
>>> Thanks,
>>>
>>>         M.
>>> --
>>> Jazz is not dead. It just smells funny...
>>
>> Hi,
>>
>> I've got this report again on linux-next 4c3c5cd02318 (Apr 5).
>>
>> It seems that it's still not fixed.
>>
>> Thanks!
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>> Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095
>>
>> CPU: 0 PID: 23095 Comm: syz-executor Not tainted
>> 4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4
>
> The fixes went into -rc6. Can you please give it a go?

Ah, OK, I assumed they were in the linux-next revision I used.

Thanks!

>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

kvm/arm64: use-after-free in kvm_vm_ioctl/vmacache_update

[Andrey Konovalov]

On Tue, Apr 11, 2017 at 5:36 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On 11/04/17 16:26, Andrey Konovalov wrote:
>> On Tue, Mar 14, 2017 at 1:26 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
>>> On 14/03/17 11:03, Suzuki K Poulose wrote:
>>>> On 13/03/17 09:58, Marc Zyngier wrote:
>>>>> On 10/03/17 18:37, Suzuki K Poulose wrote:
>>>>>> On 10/03/17 15:50, Andrey Konovalov wrote:
>>>>>>> On Fri, Mar 10, 2017 at 2:38 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>>>>>>
>>>>>>>> On linux-next commit 56b8bad5e066c23e8fa273ef5fba50bd3da2ace8 (Mar 8).
>>>>>>>>
>>>>>>>> Unfortunately I can't reproduce it.
>>>>>>>>
>>>>>>>> ==================================================================
>>>>>>>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>>> Read of size 8 at addr ffff80003b9a2040 by task syz-executor/26615
>>>>>>>>
>>>>>>>> CPU: 1 PID: 26615 Comm: syz-executor Not tainted
>>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>>> Call trace:
>>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>>> [<ffff200008383f64>] vmacache_update+0x114/0x118 mm/vmacache.c:63
>>>>>>>> [<ffff2000083a9000>] find_vma+0xf8/0x150 mm/mmap.c:2124
>>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>>> [<ffff2000080c2920>] __kvm_set_memory_region+0x3d8/0x12b8
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1026
>>>>>>>> [<ffff2000080c3838>] kvm_set_memory_region+0x38/0x58
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1075
>>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl_set_memory_region
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:1087 [inline]
>>>>>>>> [<ffff2000080c747c>] kvm_vm_ioctl+0xb94/0x1308
>>>>>>>> arch/arm64/kvm/../../../virt/kvm/kvm_main.c:2960
>>>>>>>> [<ffff20000848f928>] vfs_ioctl fs/ioctl.c:45 [inline]
>>>>>>>> [<ffff20000848f928>] do_vfs_ioctl+0x128/0xfc0 fs/ioctl.c:685
>>>>>>>> [<ffff200008490868>] SYSC_ioctl fs/ioctl.c:700 [inline]
>>>>>>>> [<ffff200008490868>] SyS_ioctl+0xa8/0xb8 fs/ioctl.c:691
>>>>>>>> [<ffff200008083f70>] el0_svc_naked+0x24/0x28
>>>>>>>>
>>>>>>>> Allocated by task 26657:
>>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:619
>>>>>>>>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:557
>>>>>>>>  slab_post_alloc_hook mm/slab.h:456 [inline]
>>>>>>>>  slab_alloc_node mm/slub.c:2718 [inline]
>>>>>>>>  slab_alloc mm/slub.c:2726 [inline]
>>>>>>>>  kmem_cache_alloc+0x144/0x230 mm/slub.c:2731
>>>>>>>>  __split_vma+0x118/0x608 mm/mmap.c:2515
>>>>>>>>  do_munmap+0x194/0x9b0 mm/mmap.c:2636
>>>>>>>> Freed by task 26657:
>>>>>>>>  save_stack_trace_tsk+0x0/0x330 arch/arm64/kernel/stacktrace.c:133
>>>>>>>>  save_stack_trace+0x20/0x30 arch/arm64/kernel/stacktrace.c:216
>>>>>>>>  save_stack mm/kasan/kasan.c:515 [inline]
>>>>>>>>  set_track mm/kasan/kasan.c:527 [inline]
>>>>>>>>  kasan_slab_free+0x84/0x198 mm/kasan/kasan.c:592
>>>>>>>>  slab_free_hook mm/slub.c:1357 [inline]
>>>>>>>>  slab_free_freelist_hook mm/slub.c:1379 [inline]
>>>>>>>>  slab_free mm/slub.c:2961 [inline]
>>>>>>>>  kmem_cache_free+0x80/0x258 mm/slub.c:2983
>>>>>>>>  __vma_adjust+0x6b0/0xf mm/mmap.c:890]  el0_svc_naked+0x24/0x28
>>>>>>>>
>>>>>>>> The buggy address belongs to the object at ffff80003b9a2000
>>>>>>>>  which belongs to the cache vm_area_struct(647:session-6.scope) of size 184
>>>>>>>> The buggy address is located 64 bytes inside of
>>>>>>>>  184-byte region [ffff80003b9a2000, ffff80003b9a20b8)
>>>>>>>> The buggy address belongs to the page:
>>>>>>>> page:ffff7e0000ee6880 count:1 mapcount:0 mapping:          (null) index:0x0
>>>>>>>> flags: 0xfffc00000000100(slab)
>>>>>>>> raw: 0fffc00000000100 0000000000000000 0000000000000000 0000000180100010
>>>>>>>> raw: 0000000000000000 0000000c00000001 ffff80005a5cc600 ffff80005ac99980
>>>>>>>> page dumped because: kasan: bad access detected
>>>>>>>> page->mem_cgroup:ffff80005ac99980
>>>>>>>>
>>>>>>>> Memory state around the buggy address:
>>>>>>>>  ffff80003b9a1f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>>  ffff80003b9a1f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>>>>>>>>> ffff80003b9a2000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>>                                            ^
>>>>>>>>  ffff80003b9a2080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb
>>>>>>>>  ffff80003b9a2100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>>>>>>> ==================================================================
>>>>>>>
>>>>>>> Another one that looks related and doesn't have parts of stack traces missing:
>>>>>>>
>>>>>>> ==================================================================
>>>>>>> BUG: KASAN: use-after-free in find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>>> Read of size 8 at addr ffff800031a03e90 by task syz-executor/4360
>>>>>>>
>>>>>>> CPU: 2 PID: 4360 Comm: syz-executor Not tainted
>>>>>>> 4.11.0-rc1-next-20170308-xc2-dirty #3
>>>>>>> Hardware name: Hardkernel ODROID-C2 (DT)
>>>>>>> Call trace:
>>>>>>> [<ffff20000808fbb0>] dump_backtrace+0x0/0x440 arch/arm64/kernel/traps.c:505
>>>>>>> [<ffff200008090010>] show_stack+0x20/0x30 arch/arm64/kernel/traps.c:228
>>>>>>> [<ffff2000088e9578>] __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>> [<ffff2000088e9578>] dump_stack+0x110/0x168 lib/dump_stack.c:52
>>>>>>> [<ffff200008414018>] print_address_description+0x60/0x248 mm/kasan/report.c:250
>>>>>>> [<ffff2000084142e8>] kasan_report_error+0xe8/0x250 mm/kasan/report.c:349
>>>>>>> [<ffff200008414564>] kasan_report mm/kasan/report.c:372 [inline]
>>>>>>> [<ffff200008414564>] __asan_report_load8_noabort+0x3c/0x48 mm/kasan/report.c:393
>>>>>>> [<ffff2000083a9048>] find_vma+0x140/0x150 mm/mmap.c:2114
>>>>>>> [<ffff2000080dc19c>] kvm_arch_prepare_memory_region+0x2ac/0x488
>>>>>>> arch/arm64/kvm/../../../arch/arm/kvm/mmu.c:1817
>>>>>>
>>>>>> It looks like we don't take the mmap_sem before calling find_vma() in
>>>>>> stage2_unmap_memslot() and in kvm_arch_prepare_memory_region(), which is causing
>>>>>> the race, with probably the test trying to unmap ranges in between.
>>>>>
>>>>> That indeed seems like a possible failure mode. The annoying thing is
>>>>> that we're not exactly in a position to take mmap_sem in
>>>>> stage2_unmap_memslot, since we hold the kvm->mmu_lock spinlock. We may
>>>>> have to hold mmap_sem while iterating over all the memslots.
>>>>>
>>>>> How about the following (very lightly tested):
>>>>>
>>>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>>>> index 962616fd4ddd..2006a79d5912 100644
>>>>> --- a/arch/arm/kvm/mmu.c
>>>>> +++ b/arch/arm/kvm/mmu.c
>>>>> @@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>>      int idx;
>>>>>
>>>>>      idx = srcu_read_lock(&kvm->srcu);
>>>>> +    down_read(&current->mm->mmap_sem);
>>>>>      spin_lock(&kvm->mmu_lock);
>>>>>
>>>>>      slots = kvm_memslots(kvm);
>>>>> @@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
>>>>>              stage2_unmap_memslot(kvm, memslot);
>>>>>
>>>>>      spin_unlock(&kvm->mmu_lock);
>>>>> +    up_read(&current->mm->mmap_sem);
>>>>>      srcu_read_unlock(&kvm->srcu, idx);
>>>>>  }
>>>>>
>>>>> @@ -1813,6 +1815,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>>       *     |               memory region                |
>>>>>       *     +--------------------------------------------+
>>>>>       */
>>>>> +    down_read(&current->mm->mmap_sem);
>>>>>      do {
>>>>>              struct vm_area_struct *vma = find_vma(current->mm, hva);
>>>>>              hva_t vm_start, vm_end;
>>>>
>>>> I have added the following hunk :
>>>>
>>>> @@ -1844,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>>>>                          pa += vm_start - vma->vm_start;
>>>>
>>>>                          /* IO region dirty page logging not allowed */
>>>> -                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
>>>> -                               return -EINVAL;
>>>> +                       if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>>>> +                               ret = -EINVAL;
>>>> +                               goto out;
>>>> +                       }
>>>>
>>>>                          ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>>>>                                                      vm_end - vm_start,
>>>>
>>>
>>> Ah, of course... Thanks for pointing that out, I'll fix it as I post a
>>> proper patch.
>>>
>>> Thanks,
>>>
>>>         M.
>>> --
>>> Jazz is not dead. It just smells funny...
>>
>> Hi,
>>
>> I've got this report again on linux-next 4c3c5cd02318 (Apr 5).
>>
>> It seems that it's still not fixed.
>>
>> Thanks!
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in vmacache_update+0x114/0x118 mm/vmacache.c:63
>> Read of size 8 at addr ffff80004d53aae8 by task syz-executor/23095
>>
>> CPU: 0 PID: 23095 Comm: syz-executor Not tainted
>> 4.11.0-rc5-next-20170405-xc2-09030-g4c3c5cd02318-dirty #4
>
> The fixes went into -rc6. Can you please give it a go?

Ah, OK, I assumed they were in the linux-next revision I used.

Thanks!

>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe at googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.