* Re: KASAN: use-after-free Read in shmem_fault (2)
[not found] <20190831045826.748-1-hdanton@sina.com>
@ 2019-09-02 13:52 ` Matthew Wilcox
2019-09-02 14:20 ` Kirill A. Shutemov
0 siblings, 1 reply; 6+ messages in thread
From: Matthew Wilcox @ 2019-09-02 13:52 UTC (permalink / raw)
To: Hillf Danton; +Cc: syzbot, hughd, linux-kernel, linux-mm, syzkaller-bugs
On Sat, Aug 31, 2019 at 12:58:26PM +0800, Hillf Danton wrote:
> On Fri, 30 Aug 2019 12:40:06 -0700
> > syzbot found the following crash on:
> >
> > HEAD commit: a55aa89a Linux 5.3-rc6
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=12f4beb6600000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
> > dashboard link: https://syzkaller.appspot.com/bug?extid=03ee87124ee05af991bd
> > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+03ee87124ee05af991bd@syzkaller.appspotmail.com
> >
> > ==================================================================
> > BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530
> > include/trace/events/lock.h:13
> > Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173
> >
> > CPU: 0 PID: 26173 Comm: syz-executor.0 Not tainted 5.3.0-rc6 #146
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> > __dump_stack lib/dump_stack.c:77 [inline]
> > dump_stack+0x172/0x1f0 lib/dump_stack.c:113
> > print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
> > __kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
> > kasan_report+0x12/0x17 mm/kasan/common.c:618
> > __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
> > perf_trace_lock_acquire+0x401/0x530 include/trace/events/lock.h:13
> > trace_lock_acquire include/trace/events/lock.h:13 [inline]
> > lock_acquire+0x2de/0x410 kernel/locking/lockdep.c:4411
> > __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> > _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151
> > spin_lock include/linux/spinlock.h:338 [inline]
> > shmem_fault+0x5ec/0x7b0 mm/shmem.c:2034
> > __do_fault+0x111/0x540 mm/memory.c:3083
> > do_shared_fault mm/memory.c:3535 [inline]
> > do_fault mm/memory.c:3613 [inline]
> > handle_pte_fault mm/memory.c:3840 [inline]
> > __handle_mm_fault+0x2adf/0x3f20 mm/memory.c:3964
> > handle_mm_fault+0x1b5/0x6b0 mm/memory.c:4001
> > do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
> > __do_page_fault+0x536/0xdd0 arch/x86/mm/fault.c:1506
> > do_page_fault+0x38/0x590 arch/x86/mm/fault.c:1530
> > page_fault+0x39/0x40 arch/x86/entry/entry_64.S:1202
> > RIP: 0010:copy_user_generic_unrolled+0x89/0xc0
> > arch/x86/lib/copy_user_64.S:91
> > Code: 38 4c 89 47 20 4c 89 4f 28 4c 89 57 30 4c 89 5f 38 48 8d 76 40 48 8d
> > 7f 40 ff c9 75 b6 89 d1 83 e2 07 c1 e9 03 74 12 4c 8b 06 <4c> 89 07 48 8d
> > 76 08 48 8d 7f 08 ff c9 75 ee 21 d2 74 10 89 d1 8a
> > RSP: 0018:ffff88806b927e18 EFLAGS: 00010202
> > RAX: 0000000000000001 RBX: 0000000000000008 RCX: 0000000000000001
> > RDX: 0000000000000000 RSI: ffff88806b927e80 RDI: 0000000020000000
> > RBP: ffff88806b927e50 R08: 0000000500000004 R09: ffffed100d724fd1
> > R10: ffffed100d724fd0 R11: ffff88806b927e87 R12: 0000000020000000
> > R13: ffff88806b927e80 R14: 0000000020000008 R15: 00007ffffffff000
> > copy_to_user include/linux/uaccess.h:152 [inline]
> > do_pipe2+0xec/0x160 fs/pipe.c:857
> > __do_sys_pipe fs/pipe.c:878 [inline]
> > __se_sys_pipe fs/pipe.c:876 [inline]
> > __x64_sys_pipe+0x33/0x40 fs/pipe.c:876
> > do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
> > entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x459879
> > Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> > 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> > ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> > RSP: 002b:00007f833e81fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000016
> > RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000459879
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000000
> > RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f833e8206d4
> > R13: 00000000004f5b47 R14: 00000000004db7b8 R15: 00000000ffffffff
> >
> > Allocated by task 25774:
> > save_stack+0x23/0x90 mm/kasan/common.c:69
> > set_track mm/kasan/common.c:77 [inline]
> > __kasan_kmalloc mm/kasan/common.c:493 [inline]
> > __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:466
> > kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:501
> > slab_post_alloc_hook mm/slab.h:520 [inline]
> > slab_alloc mm/slab.c:3319 [inline]
> > kmem_cache_alloc+0x121/0x710 mm/slab.c:3483
> > shmem_alloc_inode+0x1c/0x50 mm/shmem.c:3630
> > alloc_inode+0x68/0x1e0 fs/inode.c:227
> > new_inode_pseudo+0x19/0xf0 fs/inode.c:916
> > new_inode+0x1f/0x40 fs/inode.c:945
> > shmem_get_inode+0x84/0x7e0 mm/shmem.c:2228
> > __shmem_file_setup.part.0+0x1e2/0x2b0 mm/shmem.c:3985
> > __shmem_file_setup mm/shmem.c:3979 [inline]
> > shmem_kernel_file_setup mm/shmem.c:4015 [inline]
> > shmem_zero_setup+0xe1/0x4cc mm/shmem.c:4059
> > mmap_region+0x13d5/0x1760 mm/mmap.c:1804
> > do_mmap+0x82e/0x1090 mm/mmap.c:1561
> > do_mmap_pgoff include/linux/mm.h:2374 [inline]
> > vm_mmap_pgoff+0x1c5/0x230 mm/util.c:391
> > ksys_mmap_pgoff+0xf7/0x630 mm/mmap.c:1611
> > __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
> > __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
> > __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
> > do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
> > entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >
> > Freed by task 26359:
> > save_stack+0x23/0x90 mm/kasan/common.c:69
> > set_track mm/kasan/common.c:77 [inline]
> > __kasan_slab_free+0x102/0x150 mm/kasan/common.c:455
> > kasan_slab_free+0xe/0x10 mm/kasan/common.c:463
> > __cache_free mm/slab.c:3425 [inline]
> > kmem_cache_free+0x86/0x320 mm/slab.c:3693
> > shmem_free_in_core_inode+0x63/0xb0 mm/shmem.c:3640
> > i_callback+0x44/0x80 fs/inode.c:216
> > __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
> > rcu_do_batch kernel/rcu/tree.c:2114 [inline]
> > rcu_core+0x67f/0x1580 kernel/rcu/tree.c:2314
> > rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323
> > __do_softirq+0x262/0x98c kernel/softirq.c:292
> >
> > The buggy address belongs to the object at ffff8880a5cf2a90
> > which belongs to the cache shmem_inode_cache(17:syz0) of size 1192
> > The buggy address is located 448 bytes inside of
> > 1192-byte region [ffff8880a5cf2a90, ffff8880a5cf2f38)
> > The buggy address belongs to the page:
> > page:ffffea0002973c80 refcount:1 mapcount:0 mapping:ffff88808e1418c0
> > index:0xffff8880a5cf2ffd
> > flags: 0x1fffc0000000200(slab)
> > raw: 01fffc0000000200 ffffea0002592ec8 ffffea0002492588 ffff88808e1418c0
> > raw: ffff8880a5cf2ffd ffff8880a5cf2040 0000000100000003 0000000000000000
> > page dumped because: kasan: bad access detected
> >
> > Memory state around the buggy address:
> > ffff8880a5cf2b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8880a5cf2b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ffff8880a5cf2c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ^
> > ffff8880a5cf2c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8880a5cf2d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ==================================================================
>
>
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2021,6 +2021,12 @@ static vm_fault_t shmem_fault(struct vm_
> shmem_falloc_waitq = shmem_falloc->waitq;
> prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
> TASK_UNINTERRUPTIBLE);
> + /*
> + * it is not trivial to see what will take place after
> + * releasing i_lock and taking a nap, so hold inode to
> + * be on the safe side.
I think the comment could be improved. How about:
* The file could be unmapped by another thread after
* releasing i_lock, and the inode then freed. Hold
* a reference to the inode to prevent this.
> + */
> + __iget(inode);
> spin_unlock(&inode->i_lock);
> schedule();
>
> @@ -2034,6 +2040,7 @@ static vm_fault_t shmem_fault(struct vm_
> spin_lock(&inode->i_lock);
> finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
> spin_unlock(&inode->i_lock);
> + iput(inode);
> return ret;
> }
> spin_unlock(&inode->i_lock);
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KASAN: use-after-free Read in shmem_fault (2)
2019-09-02 13:52 ` KASAN: use-after-free Read in shmem_fault (2) Matthew Wilcox
@ 2019-09-02 14:20 ` Kirill A. Shutemov
2019-09-09 13:55 ` Matthew Wilcox
0 siblings, 1 reply; 6+ messages in thread
From: Kirill A. Shutemov @ 2019-09-02 14:20 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Hillf Danton, syzbot, hughd, linux-kernel, linux-mm, syzkaller-bugs
On Mon, Sep 02, 2019 at 06:52:54AM -0700, Matthew Wilcox wrote:
> On Sat, Aug 31, 2019 at 12:58:26PM +0800, Hillf Danton wrote:
> > On Fri, 30 Aug 2019 12:40:06 -0700
> > > syzbot found the following crash on:
> > >
> > > HEAD commit: a55aa89a Linux 5.3-rc6
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=12f4beb6600000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=03ee87124ee05af991bd
> > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > >
> > > Unfortunately, I don't have any reproducer for this crash yet.
> > >
> > > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > > Reported-by: syzbot+03ee87124ee05af991bd@syzkaller.appspotmail.com
> > >
> > > ==================================================================
> > > BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530
> > > include/trace/events/lock.h:13
> > > Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173
> > >
> > > CPU: 0 PID: 26173 Comm: syz-executor.0 Not tainted 5.3.0-rc6 #146
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > > Google 01/01/2011
> > > Call Trace:
> > > __dump_stack lib/dump_stack.c:77 [inline]
> > > dump_stack+0x172/0x1f0 lib/dump_stack.c:113
> > > print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
> > > __kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
> > > kasan_report+0x12/0x17 mm/kasan/common.c:618
> > > __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
> > > perf_trace_lock_acquire+0x401/0x530 include/trace/events/lock.h:13
> > > trace_lock_acquire include/trace/events/lock.h:13 [inline]
> > > lock_acquire+0x2de/0x410 kernel/locking/lockdep.c:4411
> > > __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> > > _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151
> > > spin_lock include/linux/spinlock.h:338 [inline]
> > > shmem_fault+0x5ec/0x7b0 mm/shmem.c:2034
> > > __do_fault+0x111/0x540 mm/memory.c:3083
> > > do_shared_fault mm/memory.c:3535 [inline]
> > > do_fault mm/memory.c:3613 [inline]
> > > handle_pte_fault mm/memory.c:3840 [inline]
> > > __handle_mm_fault+0x2adf/0x3f20 mm/memory.c:3964
> > > handle_mm_fault+0x1b5/0x6b0 mm/memory.c:4001
> > > do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
> > > __do_page_fault+0x536/0xdd0 arch/x86/mm/fault.c:1506
> > > do_page_fault+0x38/0x590 arch/x86/mm/fault.c:1530
> > > page_fault+0x39/0x40 arch/x86/entry/entry_64.S:1202
> > > RIP: 0010:copy_user_generic_unrolled+0x89/0xc0
> > > arch/x86/lib/copy_user_64.S:91
> > > Code: 38 4c 89 47 20 4c 89 4f 28 4c 89 57 30 4c 89 5f 38 48 8d 76 40 48 8d
> > > 7f 40 ff c9 75 b6 89 d1 83 e2 07 c1 e9 03 74 12 4c 8b 06 <4c> 89 07 48 8d
> > > 76 08 48 8d 7f 08 ff c9 75 ee 21 d2 74 10 89 d1 8a
> > > RSP: 0018:ffff88806b927e18 EFLAGS: 00010202
> > > RAX: 0000000000000001 RBX: 0000000000000008 RCX: 0000000000000001
> > > RDX: 0000000000000000 RSI: ffff88806b927e80 RDI: 0000000020000000
> > > RBP: ffff88806b927e50 R08: 0000000500000004 R09: ffffed100d724fd1
> > > R10: ffffed100d724fd0 R11: ffff88806b927e87 R12: 0000000020000000
> > > R13: ffff88806b927e80 R14: 0000000020000008 R15: 00007ffffffff000
> > > copy_to_user include/linux/uaccess.h:152 [inline]
> > > do_pipe2+0xec/0x160 fs/pipe.c:857
> > > __do_sys_pipe fs/pipe.c:878 [inline]
> > > __se_sys_pipe fs/pipe.c:876 [inline]
> > > __x64_sys_pipe+0x33/0x40 fs/pipe.c:876
> > > do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
> > > entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > > RIP: 0033:0x459879
> > > Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> > > 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> > > ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> > > RSP: 002b:00007f833e81fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000016
> > > RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000459879
> > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000000
> > > RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
> > > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f833e8206d4
> > > R13: 00000000004f5b47 R14: 00000000004db7b8 R15: 00000000ffffffff
> > >
> > > Allocated by task 25774:
> > > save_stack+0x23/0x90 mm/kasan/common.c:69
> > > set_track mm/kasan/common.c:77 [inline]
> > > __kasan_kmalloc mm/kasan/common.c:493 [inline]
> > > __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:466
> > > kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:501
> > > slab_post_alloc_hook mm/slab.h:520 [inline]
> > > slab_alloc mm/slab.c:3319 [inline]
> > > kmem_cache_alloc+0x121/0x710 mm/slab.c:3483
> > > shmem_alloc_inode+0x1c/0x50 mm/shmem.c:3630
> > > alloc_inode+0x68/0x1e0 fs/inode.c:227
> > > new_inode_pseudo+0x19/0xf0 fs/inode.c:916
> > > new_inode+0x1f/0x40 fs/inode.c:945
> > > shmem_get_inode+0x84/0x7e0 mm/shmem.c:2228
> > > __shmem_file_setup.part.0+0x1e2/0x2b0 mm/shmem.c:3985
> > > __shmem_file_setup mm/shmem.c:3979 [inline]
> > > shmem_kernel_file_setup mm/shmem.c:4015 [inline]
> > > shmem_zero_setup+0xe1/0x4cc mm/shmem.c:4059
> > > mmap_region+0x13d5/0x1760 mm/mmap.c:1804
> > > do_mmap+0x82e/0x1090 mm/mmap.c:1561
> > > do_mmap_pgoff include/linux/mm.h:2374 [inline]
> > > vm_mmap_pgoff+0x1c5/0x230 mm/util.c:391
> > > ksys_mmap_pgoff+0xf7/0x630 mm/mmap.c:1611
> > > __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
> > > __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
> > > __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
> > > do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
> > > entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > >
> > > Freed by task 26359:
> > > save_stack+0x23/0x90 mm/kasan/common.c:69
> > > set_track mm/kasan/common.c:77 [inline]
> > > __kasan_slab_free+0x102/0x150 mm/kasan/common.c:455
> > > kasan_slab_free+0xe/0x10 mm/kasan/common.c:463
> > > __cache_free mm/slab.c:3425 [inline]
> > > kmem_cache_free+0x86/0x320 mm/slab.c:3693
> > > shmem_free_in_core_inode+0x63/0xb0 mm/shmem.c:3640
> > > i_callback+0x44/0x80 fs/inode.c:216
> > > __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
> > > rcu_do_batch kernel/rcu/tree.c:2114 [inline]
> > > rcu_core+0x67f/0x1580 kernel/rcu/tree.c:2314
> > > rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323
> > > __do_softirq+0x262/0x98c kernel/softirq.c:292
> > >
> > > The buggy address belongs to the object at ffff8880a5cf2a90
> > > which belongs to the cache shmem_inode_cache(17:syz0) of size 1192
> > > The buggy address is located 448 bytes inside of
> > > 1192-byte region [ffff8880a5cf2a90, ffff8880a5cf2f38)
> > > The buggy address belongs to the page:
> > > page:ffffea0002973c80 refcount:1 mapcount:0 mapping:ffff88808e1418c0
> > > index:0xffff8880a5cf2ffd
> > > flags: 0x1fffc0000000200(slab)
> > > raw: 01fffc0000000200 ffffea0002592ec8 ffffea0002492588 ffff88808e1418c0
> > > raw: ffff8880a5cf2ffd ffff8880a5cf2040 0000000100000003 0000000000000000
> > > page dumped because: kasan: bad access detected
> > >
> > > Memory state around the buggy address:
> > > ffff8880a5cf2b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ffff8880a5cf2b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > ffff8880a5cf2c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ^
> > > ffff8880a5cf2c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ffff8880a5cf2d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > ==================================================================
> >
> >
> > --- a/mm/shmem.c
> > +++ b/mm/shmem.c
> > @@ -2021,6 +2021,12 @@ static vm_fault_t shmem_fault(struct vm_
> > shmem_falloc_waitq = shmem_falloc->waitq;
> > prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
> > TASK_UNINTERRUPTIBLE);
> > + /*
> > + * it is not trivial to see what will take place after
> > + * releasing i_lock and taking a nap, so hold inode to
> > + * be on the safe side.
>
> I think the comment could be improved. How about:
>
> * The file could be unmapped by another thread after
> * releasing i_lock, and the inode then freed. Hold
> * a reference to the inode to prevent this.
It only can happen if mmap_sem was released, so it's better to put
__iget() to the branch above next to up_read(). I've got confused at first
how it is possible from ->fault().
This way iput() below should only be called for ret == VM_FAULT_RETRY.
>
> > + */
> > + __iget(inode);
> > spin_unlock(&inode->i_lock);
> > schedule();
> >
> > @@ -2034,6 +2040,7 @@ static vm_fault_t shmem_fault(struct vm_
> > spin_lock(&inode->i_lock);
> > finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
> > spin_unlock(&inode->i_lock);
> > + iput(inode);
> > return ret;
> > }
> > spin_unlock(&inode->i_lock);
> >
> >
--
Kirill A. Shutemov
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KASAN: use-after-free Read in shmem_fault (2)
2019-09-02 14:20 ` Kirill A. Shutemov
@ 2019-09-09 13:55 ` Matthew Wilcox
2019-09-09 15:04 ` Kirill A. Shutemov
0 siblings, 1 reply; 6+ messages in thread
From: Matthew Wilcox @ 2019-09-09 13:55 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Hillf Danton, syzbot, hughd, linux-kernel, linux-mm, syzkaller-bugs
On Mon, Sep 02, 2019 at 05:20:30PM +0300, Kirill A. Shutemov wrote:
> On Mon, Sep 02, 2019 at 06:52:54AM -0700, Matthew Wilcox wrote:
> > On Sat, Aug 31, 2019 at 12:58:26PM +0800, Hillf Danton wrote:
> > > On Fri, 30 Aug 2019 12:40:06 -0700
> > > > syzbot found the following crash on:
> > > >
> > > > HEAD commit: a55aa89a Linux 5.3-rc6
> > > > git tree: upstream
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=12f4beb6600000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=03ee87124ee05af991bd
> > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > > >
> > > > ==================================================================
> > > > BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530
> > > > include/trace/events/lock.h:13
> > > > Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173
> > >
> > > --- a/mm/shmem.c
> > > +++ b/mm/shmem.c
> > > @@ -2021,6 +2021,12 @@ static vm_fault_t shmem_fault(struct vm_
> > > shmem_falloc_waitq = shmem_falloc->waitq;
> > > prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
> > > TASK_UNINTERRUPTIBLE);
> > > + /*
> > > + * it is not trivial to see what will take place after
> > > + * releasing i_lock and taking a nap, so hold inode to
> > > + * be on the safe side.
> >
> > I think the comment could be improved. How about:
> >
> > * The file could be unmapped by another thread after
> > * releasing i_lock, and the inode then freed. Hold
> > * a reference to the inode to prevent this.
>
> It only can happen if mmap_sem was released, so it's better to put
> __iget() to the branch above next to up_read(). I've got confused at first
> how it is possible from ->fault().
>
> This way iput() below should only be called for ret == VM_FAULT_RETRY.
Looking at the rather similar construct in filemap.c, should we solve
it the same way, where we inc the refcount on the struct file instead
of the inode before releasing the mmap_sem?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KASAN: use-after-free Read in shmem_fault (2)
2019-09-09 13:55 ` Matthew Wilcox
@ 2019-09-09 15:04 ` Kirill A. Shutemov
2019-09-17 12:08 ` Kirill A. Shutemov
0 siblings, 1 reply; 6+ messages in thread
From: Kirill A. Shutemov @ 2019-09-09 15:04 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Hillf Danton, syzbot, hughd, linux-kernel, linux-mm, syzkaller-bugs
On Mon, Sep 09, 2019 at 06:55:21AM -0700, Matthew Wilcox wrote:
> On Mon, Sep 02, 2019 at 05:20:30PM +0300, Kirill A. Shutemov wrote:
> > On Mon, Sep 02, 2019 at 06:52:54AM -0700, Matthew Wilcox wrote:
> > > On Sat, Aug 31, 2019 at 12:58:26PM +0800, Hillf Danton wrote:
> > > > On Fri, 30 Aug 2019 12:40:06 -0700
> > > > > syzbot found the following crash on:
> > > > >
> > > > > HEAD commit: a55aa89a Linux 5.3-rc6
> > > > > git tree: upstream
> > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=12f4beb6600000
> > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=03ee87124ee05af991bd
> > > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > > > >
> > > > > ==================================================================
> > > > > BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530
> > > > > include/trace/events/lock.h:13
> > > > > Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173
> > > >
> > > > --- a/mm/shmem.c
> > > > +++ b/mm/shmem.c
> > > > @@ -2021,6 +2021,12 @@ static vm_fault_t shmem_fault(struct vm_
> > > > shmem_falloc_waitq = shmem_falloc->waitq;
> > > > prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
> > > > TASK_UNINTERRUPTIBLE);
> > > > + /*
> > > > + * it is not trivial to see what will take place after
> > > > + * releasing i_lock and taking a nap, so hold inode to
> > > > + * be on the safe side.
> > >
> > > I think the comment could be improved. How about:
> > >
> > > * The file could be unmapped by another thread after
> > > * releasing i_lock, and the inode then freed. Hold
> > > * a reference to the inode to prevent this.
> >
> > It only can happen if mmap_sem was released, so it's better to put
> > __iget() to the branch above next to up_read(). I've got confused at first
> > how it is possible from ->fault().
> >
> > This way iput() below should only be called for ret == VM_FAULT_RETRY.
>
> Looking at the rather similar construct in filemap.c, should we solve
> it the same way, where we inc the refcount on the struct file instead
> of the inode before releasing the mmap_sem?
Are you talking about maybe_unlock_mmap_for_io()? Yeah, worth moving it to
mm/internal.h and reuse.
Care to prepare the patch? :P
--
Kirill A. Shutemov
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KASAN: use-after-free Read in shmem_fault (2)
2019-09-09 15:04 ` Kirill A. Shutemov
@ 2019-09-17 12:08 ` Kirill A. Shutemov
0 siblings, 0 replies; 6+ messages in thread
From: Kirill A. Shutemov @ 2019-09-17 12:08 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Hillf Danton, syzbot, hughd, linux-kernel, linux-mm, syzkaller-bugs
On Mon, Sep 09, 2019 at 06:04:12PM +0300, Kirill A. Shutemov wrote:
> On Mon, Sep 09, 2019 at 06:55:21AM -0700, Matthew Wilcox wrote:
> > On Mon, Sep 02, 2019 at 05:20:30PM +0300, Kirill A. Shutemov wrote:
> > > On Mon, Sep 02, 2019 at 06:52:54AM -0700, Matthew Wilcox wrote:
> > > > On Sat, Aug 31, 2019 at 12:58:26PM +0800, Hillf Danton wrote:
> > > > > On Fri, 30 Aug 2019 12:40:06 -0700
> > > > > > syzbot found the following crash on:
> > > > > >
> > > > > > HEAD commit: a55aa89a Linux 5.3-rc6
> > > > > > git tree: upstream
> > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=12f4beb6600000
> > > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
> > > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=03ee87124ee05af991bd
> > > > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > > > > >
> > > > > > ==================================================================
> > > > > > BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530
> > > > > > include/trace/events/lock.h:13
> > > > > > Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173
> > > > >
> > > > > --- a/mm/shmem.c
> > > > > +++ b/mm/shmem.c
> > > > > @@ -2021,6 +2021,12 @@ static vm_fault_t shmem_fault(struct vm_
> > > > > shmem_falloc_waitq = shmem_falloc->waitq;
> > > > > prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
> > > > > TASK_UNINTERRUPTIBLE);
> > > > > + /*
> > > > > + * it is not trivial to see what will take place after
> > > > > + * releasing i_lock and taking a nap, so hold inode to
> > > > > + * be on the safe side.
> > > >
> > > > I think the comment could be improved. How about:
> > > >
> > > > * The file could be unmapped by another thread after
> > > > * releasing i_lock, and the inode then freed. Hold
> > > > * a reference to the inode to prevent this.
> > >
> > > It only can happen if mmap_sem was released, so it's better to put
> > > __iget() to the branch above next to up_read(). I've got confused at first
> > > how it is possible from ->fault().
> > >
> > > This way iput() below should only be called for ret == VM_FAULT_RETRY.
> >
> > Looking at the rather similar construct in filemap.c, should we solve
> > it the same way, where we inc the refcount on the struct file instead
> > of the inode before releasing the mmap_sem?
>
> Are you talking about maybe_unlock_mmap_for_io()? Yeah, worth moving it to
> mm/internal.h and reuse.
>
> Care to prepare the patch? :P
Something like this? Untested.
diff --git a/mm/filemap.c b/mm/filemap.c
index d0cf700bf201..a542f72f57cc 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2349,26 +2349,6 @@ EXPORT_SYMBOL(generic_file_read_iter);
#ifdef CONFIG_MMU
#define MMAP_LOTSAMISS (100)
-static struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
- struct file *fpin)
-{
- int flags = vmf->flags;
-
- if (fpin)
- return fpin;
-
- /*
- * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or
- * anything, so we only pin the file and drop the mmap_sem if only
- * FAULT_FLAG_ALLOW_RETRY is set.
- */
- if ((flags & (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT)) ==
- FAULT_FLAG_ALLOW_RETRY) {
- fpin = get_file(vmf->vma->vm_file);
- up_read(&vmf->vma->vm_mm->mmap_sem);
- }
- return fpin;
-}
/*
* lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_sem
diff --git a/mm/internal.h b/mm/internal.h
index e32390802fd3..75ffa646de82 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -362,6 +362,27 @@ vma_address(struct page *page, struct vm_area_struct *vma)
return max(start, vma->vm_start);
}
+static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
+ struct file *fpin)
+{
+ int flags = vmf->flags;
+
+ if (fpin)
+ return fpin;
+
+ /*
+ * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or
+ * anything, so we only pin the file and drop the mmap_sem if only
+ * FAULT_FLAG_ALLOW_RETRY is set.
+ */
+ if ((flags & (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT)) ==
+ FAULT_FLAG_ALLOW_RETRY) {
+ fpin = get_file(vmf->vma->vm_file);
+ up_read(&vmf->vma->vm_mm->mmap_sem);
+ }
+ return fpin;
+}
+
#else /* !CONFIG_MMU */
static inline void clear_page_mlock(struct page *page) { }
static inline void mlock_vma_page(struct page *page) { }
diff --git a/mm/shmem.c b/mm/shmem.c
index 2bed4761f279..551fa49eb7f6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2007,16 +2007,14 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
shmem_falloc->waitq &&
vmf->pgoff >= shmem_falloc->start &&
vmf->pgoff < shmem_falloc->next) {
+ struct file *fpin = NULL;
wait_queue_head_t *shmem_falloc_waitq;
DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
ret = VM_FAULT_NOPAGE;
- if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
- !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
- /* It's polite to up mmap_sem if we can */
- up_read(&vma->vm_mm->mmap_sem);
+ fpin = maybe_unlock_mmap_for_io(vmf, fpin);
+ if (fpin)
ret = VM_FAULT_RETRY;
- }
shmem_falloc_waitq = shmem_falloc->waitq;
prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
@@ -2034,6 +2032,9 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
spin_lock(&inode->i_lock);
finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
spin_unlock(&inode->i_lock);
+
+ if (fpin)
+ fput(fpin);
return ret;
}
spin_unlock(&inode->i_lock);
--
Kirill A. Shutemov
^ permalink raw reply related [flat|nested] 6+ messages in thread
* KASAN: use-after-free Read in shmem_fault (2)
@ 2019-08-30 19:40 syzbot
0 siblings, 0 replies; 6+ messages in thread
From: syzbot @ 2019-08-30 19:40 UTC (permalink / raw)
To: hughd, linux-kernel, linux-mm, syzkaller-bugs
Hello,
syzbot found the following crash on:
HEAD commit: a55aa89a Linux 5.3-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12f4beb6600000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
dashboard link: https://syzkaller.appspot.com/bug?extid=03ee87124ee05af991bd
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
Unfortunately, I don't have any reproducer for this crash yet.
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+03ee87124ee05af991bd@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in perf_trace_lock_acquire+0x401/0x530
include/trace/events/lock.h:13
Read of size 8 at addr ffff8880a5cf2c50 by task syz-executor.0/26173
CPU: 0 PID: 26173 Comm: syz-executor.0 Not tainted 5.3.0-rc6 #146
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
__kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
kasan_report+0x12/0x17 mm/kasan/common.c:618
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
perf_trace_lock_acquire+0x401/0x530 include/trace/events/lock.h:13
trace_lock_acquire include/trace/events/lock.h:13 [inline]
lock_acquire+0x2de/0x410 kernel/locking/lockdep.c:4411
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:338 [inline]
shmem_fault+0x5ec/0x7b0 mm/shmem.c:2034
__do_fault+0x111/0x540 mm/memory.c:3083
do_shared_fault mm/memory.c:3535 [inline]
do_fault mm/memory.c:3613 [inline]
handle_pte_fault mm/memory.c:3840 [inline]
__handle_mm_fault+0x2adf/0x3f20 mm/memory.c:3964
handle_mm_fault+0x1b5/0x6b0 mm/memory.c:4001
do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
__do_page_fault+0x536/0xdd0 arch/x86/mm/fault.c:1506
do_page_fault+0x38/0x590 arch/x86/mm/fault.c:1530
page_fault+0x39/0x40 arch/x86/entry/entry_64.S:1202
RIP: 0010:copy_user_generic_unrolled+0x89/0xc0
arch/x86/lib/copy_user_64.S:91
Code: 38 4c 89 47 20 4c 89 4f 28 4c 89 57 30 4c 89 5f 38 48 8d 76 40 48 8d
7f 40 ff c9 75 b6 89 d1 83 e2 07 c1 e9 03 74 12 4c 8b 06 <4c> 89 07 48 8d
76 08 48 8d 7f 08 ff c9 75 ee 21 d2 74 10 89 d1 8a
RSP: 0018:ffff88806b927e18 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000008 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffff88806b927e80 RDI: 0000000020000000
RBP: ffff88806b927e50 R08: 0000000500000004 R09: ffffed100d724fd1
R10: ffffed100d724fd0 R11: ffff88806b927e87 R12: 0000000020000000
R13: ffff88806b927e80 R14: 0000000020000008 R15: 00007ffffffff000
copy_to_user include/linux/uaccess.h:152 [inline]
do_pipe2+0xec/0x160 fs/pipe.c:857
__do_sys_pipe fs/pipe.c:878 [inline]
__se_sys_pipe fs/pipe.c:876 [inline]
__x64_sys_pipe+0x33/0x40 fs/pipe.c:876
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459879
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f833e81fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000016
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000459879
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000000
RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f833e8206d4
R13: 00000000004f5b47 R14: 00000000004db7b8 R15: 00000000ffffffff
Allocated by task 25774:
save_stack+0x23/0x90 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_kmalloc mm/kasan/common.c:493 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:466
kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:501
slab_post_alloc_hook mm/slab.h:520 [inline]
slab_alloc mm/slab.c:3319 [inline]
kmem_cache_alloc+0x121/0x710 mm/slab.c:3483
shmem_alloc_inode+0x1c/0x50 mm/shmem.c:3630
alloc_inode+0x68/0x1e0 fs/inode.c:227
new_inode_pseudo+0x19/0xf0 fs/inode.c:916
new_inode+0x1f/0x40 fs/inode.c:945
shmem_get_inode+0x84/0x7e0 mm/shmem.c:2228
__shmem_file_setup.part.0+0x1e2/0x2b0 mm/shmem.c:3985
__shmem_file_setup mm/shmem.c:3979 [inline]
shmem_kernel_file_setup mm/shmem.c:4015 [inline]
shmem_zero_setup+0xe1/0x4cc mm/shmem.c:4059
mmap_region+0x13d5/0x1760 mm/mmap.c:1804
do_mmap+0x82e/0x1090 mm/mmap.c:1561
do_mmap_pgoff include/linux/mm.h:2374 [inline]
vm_mmap_pgoff+0x1c5/0x230 mm/util.c:391
ksys_mmap_pgoff+0xf7/0x630 mm/mmap.c:1611
__do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
__se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
__x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 26359:
save_stack+0x23/0x90 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:455
kasan_slab_free+0xe/0x10 mm/kasan/common.c:463
__cache_free mm/slab.c:3425 [inline]
kmem_cache_free+0x86/0x320 mm/slab.c:3693
shmem_free_in_core_inode+0x63/0xb0 mm/shmem.c:3640
i_callback+0x44/0x80 fs/inode.c:216
__rcu_reclaim kernel/rcu/rcu.h:222 [inline]
rcu_do_batch kernel/rcu/tree.c:2114 [inline]
rcu_core+0x67f/0x1580 kernel/rcu/tree.c:2314
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323
__do_softirq+0x262/0x98c kernel/softirq.c:292
The buggy address belongs to the object at ffff8880a5cf2a90
which belongs to the cache shmem_inode_cache(17:syz0) of size 1192
The buggy address is located 448 bytes inside of
1192-byte region [ffff8880a5cf2a90, ffff8880a5cf2f38)
The buggy address belongs to the page:
page:ffffea0002973c80 refcount:1 mapcount:0 mapping:ffff88808e1418c0
index:0xffff8880a5cf2ffd
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002592ec8 ffffea0002492588 ffff88808e1418c0
raw: ffff8880a5cf2ffd ffff8880a5cf2040 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8880a5cf2b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a5cf2b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a5cf2c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a5cf2c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a5cf2d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-09-17 12:08 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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[not found] <20190831045826.748-1-hdanton@sina.com>
2019-09-02 13:52 ` KASAN: use-after-free Read in shmem_fault (2) Matthew Wilcox
2019-09-02 14:20 ` Kirill A. Shutemov
2019-09-09 13:55 ` Matthew Wilcox
2019-09-09 15:04 ` Kirill A. Shutemov
2019-09-17 12:08 ` Kirill A. Shutemov
2019-08-30 19:40 syzbot
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