[syzbot] KASAN: slab-out-of-bounds Read in copy_data

[syzbot] KASAN: slab-out-of-bounds Read in copy_data

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000

The issue was bisected to:

commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
Author: Leon Romanovsky <leonro@nvidia.com>
Date:   Thu Oct 21 14:16:14 2021 +0000

    devlink: Remove not-executed trap policer notifications

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")

==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542

CPU: 1 PID: 6542 Comm: syz-executor989 Not tainted 5.15.0-rc6-next-20211025-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
 __kasan_report mm/kasan/report.c:433 [inline]
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
 memcpy+0x20/0x60 mm/kasan/shadow.c:65
 memcpy include/linux/fortify-string.h:225 [inline]
 copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
 virtio_read+0x1e0/0x230 drivers/char/hw_random/virtio-rng.c:90
 rng_get_data drivers/char/hw_random/core.c:192 [inline]
 rng_dev_read+0x400/0x660 drivers/char/hw_random/core.c:229
 vfs_read+0x1b5/0x600 fs/read_write.c:483
 ksys_read+0x12d/0x250 fs/read_write.c:623
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f05696617e9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 00 00 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 73 01 c3 48 c7 c1 c4 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd06461948 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 000000000001294d RCX: 00007f05696617e9
RDX: 00000000fffffff1 RSI: 0000000020000180 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffd064619b0 R09: 00007ffd064619b0
R10: 00007ffd064613d0 R11: 0000000000000246 R12: 00007ffd0646197c
R13: 00007ffd064619b0 R14: 00007ffd06461990 R15: 0000000000000002
 </TASK>

Allocated by task 1:
 kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 ____kasan_kmalloc mm/kasan/common.c:472 [inline]
 __kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:590 [inline]
 kzalloc include/linux/slab.h:724 [inline]
 probe_common+0xaa/0x5b0 drivers/char/hw_random/virtio-rng.c:132
 virtio_dev_probe+0x44e/0x760 drivers/virtio/virtio.c:273
 call_driver_probe drivers/base/dd.c:517 [inline]
 really_probe+0x245/0xcc0 drivers/base/dd.c:596
 __driver_probe_device+0x338/0x4d0 drivers/base/dd.c:751
 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:781
 __driver_attach+0x22d/0x4e0 drivers/base/dd.c:1140
 bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:301
 bus_add_driver+0x41d/0x630 drivers/base/bus.c:618
 driver_register+0x220/0x3a0 drivers/base/driver.c:171
 do_one_initcall+0x103/0x650 init/main.c:1303
 do_initcall_level init/main.c:1378 [inline]
 do_initcalls init/main.c:1394 [inline]
 do_basic_setup init/main.c:1413 [inline]
 kernel_init_freeable+0x6b1/0x73a init/main.c:1618
 kernel_init+0x1a/0x1d0 init/main.c:1507
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff88801a7a1400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 384 bytes inside of
 512-byte region [ffff88801a7a1400, ffff88801a7a1600)
The buggy address belongs to the page:
page:ffffea000069e800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1a7a0
head:ffffea000069e800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888010c41c80
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, ts 7709676886, free_ts 0
 prep_new_page mm/page_alloc.c:2418 [inline]
 get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4149
 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5369
 alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2036
 alloc_pages+0x29f/0x300 mm/mempolicy.c:2186
 alloc_slab_page mm/slub.c:1793 [inline]
 allocate_slab mm/slub.c:1930 [inline]
 new_slab+0x32d/0x4a0 mm/slub.c:1993
 ___slab_alloc+0x918/0xfe0 mm/slub.c:3022
 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3109
 slab_alloc_node mm/slub.c:3200 [inline]
 slab_alloc mm/slub.c:3242 [inline]
 kmem_cache_alloc_trace+0x289/0x2c0 mm/slub.c:3259
 kmalloc include/linux/slab.h:590 [inline]
 kzalloc include/linux/slab.h:724 [inline]
 device_private_init drivers/base/core.c:3238 [inline]
 device_add+0x11a7/0x1ee0 drivers/base/core.c:3288
 device_create_groups_vargs+0x203/0x280 drivers/base/core.c:4052
 device_create_with_groups+0xe3/0x120 drivers/base/core.c:4138
 misc_register+0x20a/0x690 drivers/char/misc.c:206
 register_miscdev drivers/char/hw_random/core.c:422 [inline]
 hwrng_modinit+0xd0/0x109 drivers/char/hw_random/core.c:621
 do_one_initcall+0x103/0x650 init/main.c:1303
 do_initcall_level init/main.c:1378 [inline]
 do_initcalls init/main.c:1394 [inline]
 do_basic_setup init/main.c:1413 [inline]
 kernel_init_freeable+0x6b1/0x73a init/main.c:1618
 kernel_init+0x1a/0x1d0 init/main.c:1507
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88801a7a1480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88801a7a1500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88801a7a1580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff88801a7a1600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88801a7a1680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
This report 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 issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Eric Dumazet]

On 10/26/21 9:39 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
> dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
> 
> The issue was bisected to:
> 
> commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
> Author: Leon Romanovsky <leonro@nvidia.com>
> Date:   Thu Oct 21 14:16:14 2021 +0000
> 
>     devlink: Remove not-executed trap policer notifications

More likely this came with

caaf2874ba27b92bca6f0298bf88bad94067ec37 hwrng: virtio - don't waste entropy

> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
> Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
> 
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
> BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
> Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
> 
> CPU: 1 PID: 6542 Comm: syz-executor989 Not tainted 5.15.0-rc6-next-20211025-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
>  __kasan_report mm/kasan/report.c:433 [inline]
>  kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
>  check_region_inline mm/kasan/generic.c:183 [inline]
>  kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
>  memcpy+0x20/0x60 mm/kasan/shadow.c:65
>  memcpy include/linux/fortify-string.h:225 [inline]
>  copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
>  virtio_read+0x1e0/0x230 drivers/char/hw_random/virtio-rng.c:90
>  rng_get_data drivers/char/hw_random/core.c:192 [inline]
>  rng_dev_read+0x400/0x660 drivers/char/hw_random/core.c:229
>  vfs_read+0x1b5/0x600 fs/read_write.c:483
>  ksys_read+0x12d/0x250 fs/read_write.c:623
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f05696617e9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 00 00 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 73 01 c3 48 c7 c1 c4 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffd06461948 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> RAX: ffffffffffffffda RBX: 000000000001294d RCX: 00007f05696617e9
> RDX: 00000000fffffff1 RSI: 0000000020000180 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 00007ffd064619b0 R09: 00007ffd064619b0
> R10: 00007ffd064613d0 R11: 0000000000000246 R12: 00007ffd0646197c
> R13: 00007ffd064619b0 R14: 00007ffd06461990 R15: 0000000000000002
>  </TASK>
> 
> Allocated by task 1:
>  kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:46 [inline]
>  set_alloc_info mm/kasan/common.c:434 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:513 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:472 [inline]
>  __kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:522
>  kmalloc include/linux/slab.h:590 [inline]
>  kzalloc include/linux/slab.h:724 [inline]
>  probe_common+0xaa/0x5b0 drivers/char/hw_random/virtio-rng.c:132
>  virtio_dev_probe+0x44e/0x760 drivers/virtio/virtio.c:273
>  call_driver_probe drivers/base/dd.c:517 [inline]
>  really_probe+0x245/0xcc0 drivers/base/dd.c:596
>  __driver_probe_device+0x338/0x4d0 drivers/base/dd.c:751
>  driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:781
>  __driver_attach+0x22d/0x4e0 drivers/base/dd.c:1140
>  bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:301
>  bus_add_driver+0x41d/0x630 drivers/base/bus.c:618
>  driver_register+0x220/0x3a0 drivers/base/driver.c:171
>  do_one_initcall+0x103/0x650 init/main.c:1303
>  do_initcall_level init/main.c:1378 [inline]
>  do_initcalls init/main.c:1394 [inline]
>  do_basic_setup init/main.c:1413 [inline]
>  kernel_init_freeable+0x6b1/0x73a init/main.c:1618
>  kernel_init+0x1a/0x1d0 init/main.c:1507
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> 
> The buggy address belongs to the object at ffff88801a7a1400
>  which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 384 bytes inside of
>  512-byte region [ffff88801a7a1400, ffff88801a7a1600)
> The buggy address belongs to the page:
> page:ffffea000069e800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1a7a0
> head:ffffea000069e800 order:2 compound_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888010c41c80
> raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, ts 7709676886, free_ts 0
>  prep_new_page mm/page_alloc.c:2418 [inline]
>  get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4149
>  __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5369
>  alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2036
>  alloc_pages+0x29f/0x300 mm/mempolicy.c:2186
>  alloc_slab_page mm/slub.c:1793 [inline]
>  allocate_slab mm/slub.c:1930 [inline]
>  new_slab+0x32d/0x4a0 mm/slub.c:1993
>  ___slab_alloc+0x918/0xfe0 mm/slub.c:3022
>  __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3109
>  slab_alloc_node mm/slub.c:3200 [inline]
>  slab_alloc mm/slub.c:3242 [inline]
>  kmem_cache_alloc_trace+0x289/0x2c0 mm/slub.c:3259
>  kmalloc include/linux/slab.h:590 [inline]
>  kzalloc include/linux/slab.h:724 [inline]
>  device_private_init drivers/base/core.c:3238 [inline]
>  device_add+0x11a7/0x1ee0 drivers/base/core.c:3288
>  device_create_groups_vargs+0x203/0x280 drivers/base/core.c:4052
>  device_create_with_groups+0xe3/0x120 drivers/base/core.c:4138
>  misc_register+0x20a/0x690 drivers/char/misc.c:206
>  register_miscdev drivers/char/hw_random/core.c:422 [inline]
>  hwrng_modinit+0xd0/0x109 drivers/char/hw_random/core.c:621
>  do_one_initcall+0x103/0x650 init/main.c:1303
>  do_initcall_level init/main.c:1378 [inline]
>  do_initcalls init/main.c:1394 [inline]
>  do_basic_setup init/main.c:1413 [inline]
>  kernel_init_freeable+0x6b1/0x73a init/main.c:1618
>  kernel_init+0x1a/0x1d0 init/main.c:1507
> page_owner free stack trace missing
> 
> Memory state around the buggy address:
>  ffff88801a7a1480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff88801a7a1500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ffff88801a7a1580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>                    ^
>  ffff88801a7a1600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff88801a7a1680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
> 
> 
> ---
> This report 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 issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
> 

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Laurent Vivier]

On 27/10/2021 00:34, Eric Dumazet wrote:
> 
> 
> On 10/26/21 9:39 AM, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
>> dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
>>
>> The issue was bisected to:
>>
>> commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
>> Author: Leon Romanovsky <leonro@nvidia.com>
>> Date:   Thu Oct 21 14:16:14 2021 +0000
>>
>>      devlink: Remove not-executed trap policer notifications
> 
> More likely this came with
> 
> caaf2874ba27b92bca6f0298bf88bad94067ec37 hwrng: virtio - don't waste entropy
> 

I'm going to have a look.

Thanks,
Laurent

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Michael S. Tsirkin]

On Wed, Oct 27, 2021 at 09:08:04AM +0200, Laurent Vivier wrote:
> On 27/10/2021 00:34, Eric Dumazet wrote:
> > 
> > 
> > On 10/26/21 9:39 AM, syzbot wrote:
> > > Hello,
> > > 
> > > syzbot found the following issue on:
> > > 
> > > HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
> > > git tree:       linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> > > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
> > > 
> > > The issue was bisected to:
> > > 
> > > commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
> > > Author: Leon Romanovsky <leonro@nvidia.com>
> > > Date:   Thu Oct 21 14:16:14 2021 +0000
> > > 
> > >      devlink: Remove not-executed trap policer notifications
> > 
> > More likely this came with
> > 
> > caaf2874ba27b92bca6f0298bf88bad94067ec37 hwrng: virtio - don't waste entropy
> > 
> 
> I'm going to have a look.
> 
> Thanks,
> Laurent

How bad is it if we just drop this and waste some bytes of entropy?

-- 
MST

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Laurent Vivier]

On 27/10/2021 09:20, Michael S. Tsirkin wrote:
> On Wed, Oct 27, 2021 at 09:08:04AM +0200, Laurent Vivier wrote:
>> On 27/10/2021 00:34, Eric Dumazet wrote:
>>>
>>>
>>> On 10/26/21 9:39 AM, syzbot wrote:
>>>> Hello,
>>>>
>>>> syzbot found the following issue on:
>>>>
>>>> HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
>>>> git tree:       linux-next
>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
>>>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
>>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
>>>>
>>>> The issue was bisected to:
>>>>
>>>> commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
>>>> Author: Leon Romanovsky <leonro@nvidia.com>
>>>> Date:   Thu Oct 21 14:16:14 2021 +0000
>>>>
>>>>       devlink: Remove not-executed trap policer notifications
>>>
>>> More likely this came with
>>>
>>> caaf2874ba27b92bca6f0298bf88bad94067ec37 hwrng: virtio - don't waste entropy
>>>
>>
>> I'm going to have a look.
>>
>> Thanks,
>> Laurent
> 
> How bad is it if we just drop this and waste some bytes of entropy?
> 

I don't think it's bad at all. In most of the cases we should use the full buffer.

So, you can drop, I will re-submit them later with a fix.

Thanks,
Laurent

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Laurent Vivier]

On 26/10/2021 18:39, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
> dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
> 
> The issue was bisected to:
> 
> commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
> Author: Leon Romanovsky <leonro@nvidia.com>
> Date:   Thu Oct 21 14:16:14 2021 +0000
> 
>      devlink: Remove not-executed trap policer notifications
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
> Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
> 
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
> BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
> Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
> 

I'm not able to reproduce the problem with next-20211026 and the C reproducer.

And reviewing the code in copy_data() I don't see any issue.

Is it possible to know what it the VM configuration used to test it?

Thanks,
Laurent

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Dmitry Vyukov]

On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <lvivier@redhat.com> wrote:
>
> On 26/10/2021 18:39, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
> > dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
> >
> > The issue was bisected to:
> >
> > commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
> > Author: Leon Romanovsky <leonro@nvidia.com>
> > Date:   Thu Oct 21 14:16:14 2021 +0000
> >
> >      devlink: Remove not-executed trap policer notifications
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
> > Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
> >
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
> > BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
> > Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
> >
>
> I'm not able to reproduce the problem with next-20211026 and the C reproducer.
>
> And reviewing the code in copy_data() I don't see any issue.
>
> Is it possible to know what it the VM configuration used to test it?

Hi Laurent,

syzbot used e2-standard-2 GCE VM when that happened.
You can see some info about these VMs under the "VM info" link on the dashboard.

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Michael S. Tsirkin]

On Wed, Oct 27, 2021 at 03:36:19PM +0200, Dmitry Vyukov wrote:
> On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <lvivier@redhat.com> wrote:
> >
> > On 26/10/2021 18:39, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
> > > git tree:       linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> > > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
> > >
> > > The issue was bisected to:
> > >
> > > commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
> > > Author: Leon Romanovsky <leonro@nvidia.com>
> > > Date:   Thu Oct 21 14:16:14 2021 +0000
> > >
> > >      devlink: Remove not-executed trap policer notifications
> > >
> > > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
> > > final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
> > > Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
> > >
> > > ==================================================================
> > > BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
> > > BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
> > > Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
> > >
> >
> > I'm not able to reproduce the problem with next-20211026 and the C reproducer.
> >
> > And reviewing the code in copy_data() I don't see any issue.
> >
> > Is it possible to know what it the VM configuration used to test it?
> 
> Hi Laurent,
> 
> syzbot used e2-standard-2 GCE VM when that happened.
> You can see some info about these VMs under the "VM info" link on the dashboard.

Could you pls confirm whether reverting
caaf2874ba27b92bca6f0298bf88bad94067ec37 addresses this?

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Laurent Vivier]

On 27/10/2021 17:28, Michael S. Tsirkin wrote:
> On Wed, Oct 27, 2021 at 03:36:19PM +0200, Dmitry Vyukov wrote:
>> On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <lvivier@redhat.com> wrote:
>>>
>>> On 26/10/2021 18:39, syzbot wrote:
>>>> Hello,
>>>>
>>>> syzbot found the following issue on:
>>>>
>>>> HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
>>>> git tree:       linux-next
>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
>>>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
>>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
>>>>
>>>> The issue was bisected to:
>>>>
>>>> commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
>>>> Author: Leon Romanovsky <leonro@nvidia.com>
>>>> Date:   Thu Oct 21 14:16:14 2021 +0000
>>>>
>>>>       devlink: Remove not-executed trap policer notifications
>>>>
>>>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
>>>> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
>>>>
>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>> Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
>>>> Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
>>>>
>>>> ==================================================================
>>>> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
>>>> BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
>>>> Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
>>>>
>>>
>>> I'm not able to reproduce the problem with next-20211026 and the C reproducer.
>>>
>>> And reviewing the code in copy_data() I don't see any issue.
>>>
>>> Is it possible to know what it the VM configuration used to test it?
>>
>> Hi Laurent,
>>
>> syzbot used e2-standard-2 GCE VM when that happened.
>> You can see some info about these VMs under the "VM info" link on the dashboard.
> 
> Could you pls confirm whether reverting
> caaf2874ba27b92bca6f0298bf88bad94067ec37 addresses this?
> 

I've restarted the syzbot on top of "hwrng: virtio - don't wait on cleanup" [1] and the 
problem has not been triggered.

See https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446

Thanks,
Laurent

[1]
d721abbeb145 hwrng: virtio - don't wait on cleanup
bb768beb0a5f hwrng: virtio - add an internal buffer
d25f27432f80 (origin/master, origin/HEAD, master) Merge tag 'arm-soc-fixes-5.15-3' of 
git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Laurent Vivier]

On 27/10/2021 18:25, Laurent Vivier wrote:
> On 27/10/2021 17:28, Michael S. Tsirkin wrote:
>> On Wed, Oct 27, 2021 at 03:36:19PM +0200, Dmitry Vyukov wrote:
>>> On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <lvivier@redhat.com> wrote:
>>>>
>>>> On 26/10/2021 18:39, syzbot wrote:
>>>>> Hello,
>>>>>
>>>>> syzbot found the following issue on:
>>>>>
>>>>> HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
>>>>> git tree:       linux-next
>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
>>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
>>>>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for 
>>>>> Debian) 2.35.2
>>>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
>>>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
>>>>>
>>>>> The issue was bisected to:
>>>>>
>>>>> commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
>>>>> Author: Leon Romanovsky <leonro@nvidia.com>
>>>>> Date:   Thu Oct 21 14:16:14 2021 +0000
>>>>>
>>>>>       devlink: Remove not-executed trap policer notifications
>>>>>
>>>>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
>>>>> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
>>>>>
>>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>>> Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
>>>>> Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
>>>>>
>>>>> ==================================================================
>>>>> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
>>>>> BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 
>>>>> drivers/char/hw_random/virtio-rng.c:68
>>>>> Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
>>>>>
>>>>
>>>> I'm not able to reproduce the problem with next-20211026 and the C reproducer.
>>>>
>>>> And reviewing the code in copy_data() I don't see any issue.
>>>>
>>>> Is it possible to know what it the VM configuration used to test it?
>>>
>>> Hi Laurent,
>>>
>>> syzbot used e2-standard-2 GCE VM when that happened.
>>> You can see some info about these VMs under the "VM info" link on the dashboard.
>>
>> Could you pls confirm whether reverting
>> caaf2874ba27b92bca6f0298bf88bad94067ec37 addresses this?
>>
> 
> I've restarted the syzbot on top of "hwrng: virtio - don't wait on cleanup" [1] and the 
> problem has not been triggered.
> 
> See https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446

The problem seems to be introduced by the last patch:

"hwrng: virtio - always add a pending request"

not

"hwrng: virtio - don't waste entropy"

Thanks,
Laurent

> 
> Thanks,
> Laurent
> 
> [1]
> d721abbeb145 hwrng: virtio - don't wait on cleanup
> bb768beb0a5f hwrng: virtio - add an internal buffer
> d25f27432f80 (origin/master, origin/HEAD, master) Merge tag 'arm-soc-fixes-5.15-3' of 
> git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc
> 

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Laurent Vivier]

On 27/10/2021 19:03, Laurent Vivier wrote:
> On 27/10/2021 18:25, Laurent Vivier wrote:
>> On 27/10/2021 17:28, Michael S. Tsirkin wrote:
>>> On Wed, Oct 27, 2021 at 03:36:19PM +0200, Dmitry Vyukov wrote:
>>>> On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <lvivier@redhat.com> wrote:
>>>>>
>>>>> On 26/10/2021 18:39, syzbot wrote:
>>>>>> Hello,
>>>>>>
>>>>>> syzbot found the following issue on:
>>>>>>
>>>>>> HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
>>>>>> git tree:       linux-next
>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
>>>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
>>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
>>>>>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for 
>>>>>> Debian) 2.35.2
>>>>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
>>>>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
>>>>>>
>>>>>> The issue was bisected to:
>>>>>>
>>>>>> commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
>>>>>> Author: Leon Romanovsky <leonro@nvidia.com>
>>>>>> Date:   Thu Oct 21 14:16:14 2021 +0000
>>>>>>
>>>>>>       devlink: Remove not-executed trap policer notifications
>>>>>>
>>>>>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
>>>>>> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
>>>>>>
>>>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>>>> Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
>>>>>> Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
>>>>>> BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 
>>>>>> drivers/char/hw_random/virtio-rng.c:68
>>>>>> Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
>>>>>>
>>>>>
>>>>> I'm not able to reproduce the problem with next-20211026 and the C reproducer.
>>>>>
>>>>> And reviewing the code in copy_data() I don't see any issue.
>>>>>
>>>>> Is it possible to know what it the VM configuration used to test it?
>>>>
>>>> Hi Laurent,
>>>>
>>>> syzbot used e2-standard-2 GCE VM when that happened.
>>>> You can see some info about these VMs under the "VM info" link on the dashboard.
>>>
>>> Could you pls confirm whether reverting
>>> caaf2874ba27b92bca6f0298bf88bad94067ec37 addresses this?
>>>
>>
>> I've restarted the syzbot on top of "hwrng: virtio - don't wait on cleanup" [1] and the 
>> problem has not been triggered.
>>
>> See https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> 
> The problem seems to be introduced by the last patch:
> 
> "hwrng: virtio - always add a pending request"

I think I understand the problem.

As we check data_avail != 0 before waiting on the completion, we can have a data_idx != 0.

The following change fixes the problem for me:

--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -52,6 +52,8 @@ static void request_entropy(struct virtrng_info *vi)
         struct scatterlist sg;

         reinit_completion(&vi->have_data);
+       vi->data_avail = 0;
+       vi->data_idx = 0;

         sg_init_one(&sg, vi->data, sizeof(vi->data));


MST, do you update the patch or do you want I send a new version?

Thanks,
Laurent

Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

[Michael S. Tsirkin]

On Wed, Oct 27, 2021 at 08:20:08PM +0200, Laurent Vivier wrote:
> On 27/10/2021 19:03, Laurent Vivier wrote:
> > On 27/10/2021 18:25, Laurent Vivier wrote:
> > > On 27/10/2021 17:28, Michael S. Tsirkin wrote:
> > > > On Wed, Oct 27, 2021 at 03:36:19PM +0200, Dmitry Vyukov wrote:
> > > > > On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <lvivier@redhat.com> wrote:
> > > > > > 
> > > > > > On 26/10/2021 18:39, syzbot wrote:
> > > > > > > Hello,
> > > > > > > 
> > > > > > > syzbot found the following issue on:
> > > > > > > 
> > > > > > > HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
> > > > > > > git tree:       linux-next
> > > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
> > > > > > > kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
> > > > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> > > > > > > compiler:       gcc (Debian 10.2.1-6) 10.2.1
> > > > > > > 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > > > > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
> > > > > > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
> > > > > > > 
> > > > > > > The issue was bisected to:
> > > > > > > 
> > > > > > > commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
> > > > > > > Author: Leon Romanovsky <leonro@nvidia.com>
> > > > > > > Date:   Thu Oct 21 14:16:14 2021 +0000
> > > > > > > 
> > > > > > >       devlink: Remove not-executed trap policer notifications
> > > > > > > 
> > > > > > > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
> > > > > > > final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
> > > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
> > > > > > > 
> > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > > > > Reported-by: syzbot+b86736b5935e0d25b446@syzkaller.appspotmail.com
> > > > > > > Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
> > > > > > > 
> > > > > > > ==================================================================
> > > > > > > BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
> > > > > > > BUG: KASAN: slab-out-of-bounds in
> > > > > > > copy_data+0xf3/0x2e0
> > > > > > > drivers/char/hw_random/virtio-rng.c:68
> > > > > > > Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
> > > > > > > 
> > > > > > 
> > > > > > I'm not able to reproduce the problem with next-20211026 and the C reproducer.
> > > > > > 
> > > > > > And reviewing the code in copy_data() I don't see any issue.
> > > > > > 
> > > > > > Is it possible to know what it the VM configuration used to test it?
> > > > > 
> > > > > Hi Laurent,
> > > > > 
> > > > > syzbot used e2-standard-2 GCE VM when that happened.
> > > > > You can see some info about these VMs under the "VM info" link on the dashboard.
> > > > 
> > > > Could you pls confirm whether reverting
> > > > caaf2874ba27b92bca6f0298bf88bad94067ec37 addresses this?
> > > > 
> > > 
> > > I've restarted the syzbot on top of "hwrng: virtio - don't wait on
> > > cleanup" [1] and the problem has not been triggered.
> > > 
> > > See https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> > 
> > The problem seems to be introduced by the last patch:
> > 
> > "hwrng: virtio - always add a pending request"
> 
> I think I understand the problem.
> 
> As we check data_avail != 0 before waiting on the completion, we can have a data_idx != 0.
> 
> The following change fixes the problem for me:
> 
> --- a/drivers/char/hw_random/virtio-rng.c
> +++ b/drivers/char/hw_random/virtio-rng.c
> @@ -52,6 +52,8 @@ static void request_entropy(struct virtrng_info *vi)
>         struct scatterlist sg;
> 
>         reinit_completion(&vi->have_data);
> +       vi->data_avail = 0;
> +       vi->data_idx = 0;
> 
>         sg_init_one(&sg, vi->data, sizeof(vi->data));
> 
> 
> MST, do you update the patch or do you want I send a new version?
> 
> Thanks,
> Laurent

New version of the patchset pls, and note in the changelog
that just this patch changed.

-- 
MST