Kernel WARNING at

Mon Nov 8 10:14:15 UTC 2021

Mhm, good question. Looks like a refcount leak somewhere.

Is that reproducible? If yes could you bisect?

In general I suggest to try to reproduce it on the latest bleeding edge 
code first.

Thanks for the notice,
Christian.

Am 05.11.21 um 04:13 schrieb Zzy Wysm:
> Another use-after-free on the same computer that looks like it’s in amdgpu:
>
> [ 2101.168138] ------------[ cut here ]------------
> [ 2101.168144] refcount_t: underflow; use-after-free.
> [ 2101.168162] WARNING: CPU: 4 PID: 965 at lib/refcount.c:28 refcount_warn_saturate+0xa6/0xf0
> [ 2101.168167] CPU: 4 PID: 965 Comm: Xorg Tainted: G                T 5.10.77 #1
> [ 2101.168169] Hardware name: Supermicro Super Server/H11SSL-NC, BIOS 2.1 02/21/2020
> [ 2101.168174] RIP: 0010:refcount_warn_saturate+0xa6/0xf0
> [ 2101.168177] Code: 05 9f 6b f3 01 01 e8 4a 0d 9d 00 0f 0b c3 80 3d 8d 6b f3 01 00 75 95 48 c7 c7 e0 ee fc ad c6 05 7d 6b f3 01 01 e8 2b 0d 9d 00 <0f> 0b c3 80 3d 6c 6b f3 01 00 0f 85 72 ff ff ff 48 c7 c7 38 ef fc
> [ 2101.168180] RSP: 0018:ffffb3778216fdc0 EFLAGS: 00010282
> [ 2101.168183] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000027
> [ 2101.168186] RDX: 0000000000000027 RSI: 00000000fffeffff RDI: ffff8ddb4e212ec8
> [ 2101.168187] RBP: ffff8dbdf149f680 R08: ffff8ddb4e212ec0 R09: ffffb3778216fbe8
> [ 2101.168189] R10: 0000000000000001 R11: 0000000000000001 R12: 00000000ffffffff
> [ 2101.168191] R13: ffff8dbca0b50c00 R14: ffff8dbca0b50c58 R15: 0000000000000000
> [ 2101.168194] FS:  000071af94f3fa40(0000) GS:ffff8ddb4e200000(0000) knlGS:0000000000000000
> [ 2101.168196] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 2101.168198] CR2: 000071af0c7a9000 CR3: 00000015680a2000 CR4: 0000000000350ee0
> [ 2101.168199] Call Trace:
> [ 2101.168206]  dma_resv_list_free.part.0+0x66/0x70
> [ 2101.168212]  drm_gem_object_release+0x28/0x50
> [ 2101.168218]  amdgpu_bo_destroy+0x60/0x100
> [ 2101.168223]  ttm_bo_release+0x1de/0x310
> [ 2101.168226]  amdgpu_bo_unref+0x15/0x20
> [ 2101.168230]  amdgpu_gem_object_free+0x2b/0x50
> [ 2101.168236]  drm_gem_dmabuf_release+0x31/0x50
> [ 2101.168239]  dma_buf_release+0x35/0x70
> [ 2101.168244]  __dentry_kill+0xe5/0x150
> [ 2101.168249]  __fput+0xe1/0x250
> [ 2101.168254]  task_work_run+0x5a/0x90
> [ 2101.168260]  exit_to_user_mode_prepare+0xbe/0xc0
> [ 2101.168266]  syscall_exit_to_user_mode+0x22/0xf0
> [ 2101.168271]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 2101.168274] RIP: 0033:0x71af953aacc7
> [ 2101.168278] Code: 00 00 00 48 8b 05 c9 91 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 99 91 0c 00 f7 d8 64 89 01 48
> [ 2101.168280] RSP: 002b:00007ffd1fbd3628 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [ 2101.168284] RAX: 0000000000000000 RBX: 00007ffd1fbd3660 RCX: 000071af953aacc7
> [ 2101.168286] RDX: 00007ffd1fbd3660 RSI: 0000000040086409 RDI: 0000000000000010
> [ 2101.168288] RBP: 0000000040086409 R08: 0000000000000007 R09: 000000000000000e
> [ 2101.168290] R10: 000000000000001b R11: 0000000000000246 R12: 0000561c5b999b98
> [ 2101.168292] R13: 0000000000000010 R14: 0000561c5ba2b72c R15: 00007ffd1fbd36a0
> [ 2101.168295] ---[ end trace 921c49c63d8e1053 ]—
>
> zzy
>
>
>> On Nov 4, 2021, at 9:34 PM, Zzy Wysm <zzy at zzywysm.com> wrote:
>>
>> I found the following warning in my log this evening.  I don’t know if or how it can be reproduced.
>>
>> Linux 5.10.77 amd64.  Kernel config attached.  (The kernel taint is merely because of the struct randomization plugin.)
>>
>> zzy
>>
>> ..
>>
>> kernel: ------------[ cut here ]------------
>> kernel: refcount_t: addition on 0; use-after-free.
>> kernel: WARNING: CPU: 3 PID: 957 at lib/refcount.c:25 refcount_warn_saturate+0x68/0xf0
>> kernel: CPU: 3 PID: 957 Comm: Xorg Tainted: G        W       T 5.10.77 #1
>> kernel: Hardware name: Supermicro Super Server/H11SSL-NC, BIOS 2.1 02/21/2020
>> kernel: RIP: 0010:refcount_warn_saturate+0x68/0xf0
>> kernel: Code: 05 2c 9f f5 01 01 e8 83 82 9e 00 0f 0b c3 80 3d 1c 9f f5 01 00 75 d3 48 c7 c7 f0 2e 1d 96 c6 05 0c 9f f5 01 01 e8 64 82 9e 00 <0f> 0b c3 80 3d ff 9e f5 01 00 75 d3 48 c7 c7 f0 2e 1d 96 c6 05 0c 9f f5 01 01 e8 64 82 9e 00 <0f> 0b c3 80 3d ff 9e f5 01 00 75 b4 48 c7 c7 c8 2e 1d 96 c6 05 ef
>> kernel: RSP: 0018:ffffb4f201cc3c00 EFLAGS: 00010286
>> kernel: RAX: 0000000000000000 RBX: ffff8a0c00ede458 RCX: 0000000000000027
>> kernel: RDX: 0000000000000027 RSI: 00000000fffeffff RDI: ffff8a2ace192e88
>> kernel: RBP: ffffb4f201cc3d38 R08: ffff8a2ace192e80 R09: ffffb4f201cc3a28
>> kernel: R10: 0000000000000001 R11: 0000000000000001 R12: ffff8a0c911e5000
>> kernel: R13: ffff8a0cba1fc580 R14: ffffb4f201cc3cc8 R15: ffff8a0c1a440000
>> kernel: FS:  0000000000000000(0000) GS:ffff8a2ace180000(0000) knlGS:0000000000000000
>> kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> kernel: CR2: 0000736ef80ab660 CR3: 00000011da80c000 CR4: 0000000000350ee0
>> kernel: Call Trace:
>> kernel:  dma_resv_add_shared_fence+0x122/0x180
>> kernel:  amdgpu_gem_object_close+0x1c3/0x250
>> kernel:  drm_gem_object_release_handle+0x2b/0x90
>> kernel:  ? drm_gem_object_handle_put_unlocked+0xc0/0xc0
>> kernel:  idr_for_each+0x70/0xe0
>> kernel:  drm_gem_release+0x17/0x20
>> kernel:  drm_file_free.part.0+0x273/0x280
>> kernel:  drm_release+0x60/0xe0
>> kernel:  __fput+0x96/0x240
>> kernel:  task_work_run+0x5a/0x90
>> kernel:  do_exit+0x34e/0xaf0
>> kernel:  do_group_exit+0x34/0xb0
>> kernel:  __x64_sys_exit_group+0xf/0x10
>> kernel:  do_syscall_64+0x33/0x40
>> kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> kernel: RIP: 0033:0x736f1c33a699
>> kernel: Code: Unable to access opcode bytes at RIP 0x736f1c33a66f.
>> kernel: RSP: 002b:00007ffce40b21e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
>> kernel: RAX: ffffffffffffffda RBX: 0000736f1c42f610 RCX: 0000736f1c33a699
>> kernel: RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
>> kernel: RBP: 0000000000000000 R08: fffffffffffffc80 R09: 0000000000000000
>> kernel: R10: 0000736f1cdbaa40 R11: 0000000000000246 R12: 0000736f1c42f610
>> kernel: R13: 0000000000000b14 R14: 0000736f1c42fae8 R15: 0000000000000000
>> kernel: ---[ end trace 52a8b244b766437f ]—
>>
>> ..
>>
>> <kernel-warning-config>
>>