[syzbot] [bcachefs?] UBSAN: array-index-out-of-bounds in lock_timer_base

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 83814698cf48 Merge tag 'powerpc-6.10-2' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1654ce06980000
kernel config: https://syzkaller.appspot.com/x/.config?x=733cc7a95171d8e7
dashboard link: https://syzkaller.appspot.com/bug?extid=6a038377f0a594d7d44e
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-83814698.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7042fdcb685d/vmlinux-83814698.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9f795e13834f/bzImage-83814698.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6a0383...@syzkaller.appspotmail.com

bcachefs (loop0): shutdown complete, journal seq 18
bcachefs (loop0): marking filesystem clean
bcachefs (loop0): shutdown complete
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in kernel/time/timer.c:962:9
index 24 is out of range for type 'long unsigned int [8]'
CPU: 0 PID: 11510 Comm: syz-executor.0 Not tainted 6.10.0-rc1-syzkaller-00304-g83814698cf48 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:114
ubsan_epilogue lib/ubsan.c:231 [inline]
__ubsan_handle_out_of_bounds+0x110/0x150 lib/ubsan.c:429
get_timer_cpu_base kernel/time/timer.c:962 [inline]
get_timer_base kernel/time/timer.c:991 [inline]
lock_timer_base+0x206/0x220 kernel/time/timer.c:1050
__try_to_del_timer_sync+0x8d/0x170 kernel/time/timer.c:1506
__timer_delete_sync+0xf4/0x1b0 kernel/time/timer.c:1665
del_timer_sync include/linux/timer.h:185 [inline]
cleanup_srcu_struct+0x124/0x520 kernel/rcu/srcutree.c:659
bch2_fs_btree_iter_exit+0x46e/0x630 fs/bcachefs/btree_iter.c:3410
__bch2_fs_free fs/bcachefs/super.c:556 [inline]
bch2_fs_release+0x117/0x820 fs/bcachefs/super.c:603
kobject_cleanup lib/kobject.c:689 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x1fa/0x5b0 lib/kobject.c:737
deactivate_locked_super+0xbe/0x1a0 fs/super.c:473
deactivate_super+0xde/0x100 fs/super.c:506
cleanup_mnt+0x222/0x450 fs/namespace.c:1267
task_work_run+0x14e/0x250 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x278/0x2a0 kernel/entry/common.c:218
__do_fast_syscall_32+0x80/0x120 arch/x86/entry/common.c:389
do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf72bc579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000ffba0958 EFLAGS: 00000292 ORIG_RAX: 0000000000000034
RAX: 0000000000000000 RBX: 00000000ffba0a00 RCX: 0000000000000009
RDX: 00000000f7412ff4 RSI: 00000000f7363361 RDI: 00000000ffba1aa4
RBP: 00000000ffba0a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
---[ end trace ]---
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 10 06 adc %al,(%rsi)
2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
6: 10 07 adc %al,(%rdi)
8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
c: 10 08 adc %cl,(%rax)
e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
1e: 00 51 52 add %dl,0x52(%rcx)
21: 55 push %rbp
22: 89 e5 mov %esp,%ebp
24: 0f 34 sysenter
26: cd 80 int $0x80
* 28: 5d pop %rbp <-- trapping instruction
29: 5a pop %rdx
2a: 59 pop %rcx
2b: c3 ret
2c: 90 nop
2d: 90 nop
2e: 90 nop
2f: 90 nop
30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi


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