WARNING: ODEBUG bug in exit_to_usermode_loop

Status: fixed on 2020/10/05 13:19
Fix commit: c5c6e00f6cc5 fix regression in "epoll: Keep a reference on files added to the check list"
First crash: 1277d, last: 1275d
Fix bisection: fixed by (bisect log) :
commit c5c6e00f6cc5d3ed0d6464b14e33f2f5c8505888
Author: Al Viro <>
Date: Wed Sep 2 15:30:48 2020 +0000

  fix regression in "epoll: Keep a reference on files added to the check list"

Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 WARNING: ODEBUG bug in exit_to_usermode_loop syz done 2 1273d 1275d 1/1 fixed on 2020/10/07 06:25

Sample crash report:
ODEBUG: free active (active state 1) object type: rcu_head hint:           (null)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 16655 at lib/debugobjects.c:287 debug_print_object.cold+0xa7/0xdb lib/debugobjects.c:287
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 16655 Comm: syz-executor.0 Not tainted 4.14.196-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 panic+0x1f9/0x42d kernel/panic.c:183
 __warn.cold+0x20/0x4b kernel/panic.c:547
 report_bug+0x208/0x249 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:177 [inline]
 fixup_bug arch/x86/kernel/traps.c:172 [inline]
 do_error_trap+0x195/0x2d0 arch/x86/kernel/traps.c:295
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:debug_print_object.cold+0xa7/0xdb lib/debugobjects.c:287
RSP: 0018:ffff888082c4fd30 EFLAGS: 00010082
RAX: 0000000000000051 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff86ac12c0 RDI: ffffed1010589f9c
RBP: ffffffff86ab6440 R08: 0000000000000051 R09: 0000000000000000
R10: 0000000000000000 R11: ffff88809ede86c0 R12: 0000000000000000
R13: 0000000000000001 R14: ffff8880a73b0000 R15: ffff8880a8bfdce8
 __debug_check_no_obj_freed lib/debugobjects.c:747 [inline]
 debug_check_no_obj_freed+0x3b7/0x674 lib/debugobjects.c:776
 kmem_cache_free+0x156/0x2b0 mm/slab.c:3757
 task_work_run+0x11f/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
RIP: 0033:0x45d5b9
RSP: 002b:00007fbd051a5c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000e9
RAX: 0000000000000000 RBX: 0000000000002ac0 RCX: 000000000045d5b9
RDX: 0000000000000003 RSI: 0000000000000001 RDI: 0000000000000005
RBP: 000000000118cf88 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020000100 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007fffb68c357f R14: 00007fbd051a69c0 R15: 000000000118cf4c


Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/09/04 11:41 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config console log report syz ci2-linux-4-14
2020/09/02 11:22 linux-4.14.y d7e78d08fa77 abf9ba4f .config console log report syz ci2-linux-4-14
* Struck through repros no longer work on HEAD.