[syzbot] [sound?] WARNING: ODEBUG bug in dummy_pcm_close
From: syzbot
Date: Wed Aug 26 2026 - 12:02:22 EST
Hello,
syzbot found the following issue on:
HEAD commit: 66498c75b4f8 Merge tag 'dmaengine-7.3-rc1' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123b9979580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e9ce1d694820ba2b
dashboard link: https://syzkaller.appspot.com/bug?extid=225231fce6755d40d078
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12b29415580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d0a47f9dd2f2/disk-66498c75.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9d5e64d02b84/vmlinux-66498c75.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f14557ff09c4/bzImage-66498c75.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+225231fce6755d40d078@xxxxxxxxxxxxxxxxxxxxxxxxx
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ODEBUG: free active (active state 0) object: ffff8880213f7f20 object type: hrtimer hint: dummy_hrtimer_callback+0x0/0x150 sound/drivers/dummy.c:-1
WARNING: lib/debugobjects.c:632 at debug_print_object+0xec/0x230 lib/debugobjects.c:629, CPU#1: syz.0.66/5973
Modules linked in:
CPU: 1 UID: 0 PID: 5973 Comm: syz.0.66 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:debug_print_object+0x18a/0x230 lib/debugobjects.c:629
Code: f8 48 c1 e8 03 80 3c 18 00 74 08 4c 89 ff e8 3d 70 4f fd 4d 8b 0f 4c 89 ef 48 8b 74 24 08 48 89 ea 44 89 e1 4d 89 f0 ff 34 24 <67> 48 0f b9 3a 48 83 c4 08 ff 05 73 77 92 0b 48 83 c4 10 5b 41 5c
RSP: 0018:ffffc90003a37b70 EFLAGS: 00010246
RAX: 1ffffffff181f12c RBX: dffffc0000000000 RCX: 0000000000000000
RDX: ffffffff8c6d6340 RSI: ffffffff8c6d5dc0 RDI: ffffffff9084dfc0
RBP: ffffffff8c6d6340 R08: ffff8880213f7f20 R09: ffffffff8c0f8ba0
R10: dffffc0000000000 R11: ffffffff81b3d530 R12: 0000000000000000
R13: ffffffff9084dfc0 R14: ffff8880213f7f20 R15: ffffffff8c0f8960
FS: 000055557a276500(0000) GS:ffff888124df1000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc4e5ef7d58 CR3: 000000007ed3e000 CR4: 00000000003526f0
Call Trace:
<TASK>
__debug_check_no_obj_freed lib/debugobjects.c:1171 [inline]
debug_check_no_obj_freed+0x2e3/0x450 lib/debugobjects.c:1201
slab_free_hook mm/slub.c:2679 [inline]
slab_free mm/slub.c:6499 [inline]
kfree+0x13e/0x650 mm/slub.c:6792
dummy_pcm_close+0x9b/0xb0 sound/drivers/dummy.c:609
snd_pcm_release_substream+0x313/0x490 sound/core/pcm_native.c:2793
snd_pcm_release+0xb6/0x160 sound/core/pcm_native.c:2983
__fput+0x418/0xa50 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
exit_to_user_mode_loop+0x204/0x770 kernel/entry/common.c:101
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc4e4f9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc47a4ba18 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fc4e5227da0 RCX: 00007fc4e4f9e0d9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fc4e5227da0 R08: 00007fc4e5226038 R09: 0000000000000000
R10: 000000000003fdc0 R11: 0000000000000246 R12: 00000000000175a9
R13: 00007fc4e522609c R14: 000000000001729d R15: 00007fc4e5226090
</TASK>
----------------
Code disassembly (best guess):
0: f8 clc
1: 48 c1 e8 03 shr $0x3,%rax
5: 80 3c 18 00 cmpb $0x0,(%rax,%rbx,1)
9: 74 08 je 0x13
b: 4c 89 ff mov %r15,%rdi
e: e8 3d 70 4f fd call 0xfd4f7050
13: 4d 8b 0f mov (%r15),%r9
16: 4c 89 ef mov %r13,%rdi
19: 48 8b 74 24 08 mov 0x8(%rsp),%rsi
1e: 48 89 ea mov %rbp,%rdx
21: 44 89 e1 mov %r12d,%ecx
24: 4d 89 f0 mov %r14,%r8
27: ff 34 24 push (%rsp)
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 48 83 c4 08 add $0x8,%rsp
33: ff 05 73 77 92 0b incl 0xb927773(%rip) # 0xb9277ac
39: 48 83 c4 10 add $0x10,%rsp
3d: 5b pop %rbx
3e: 41 5c pop %r12
---
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