[v6.1] BUG: spinlock bad magic in btrfs_encoded_read_endio

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f2ddafa93a25 Linux 6.1.166
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14031e02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=7f7402e6db0d5687291e
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5d86a86f0032/disk-f2ddafa9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aafc10ea040b/vmlinux-f2ddafa9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f6b46858e7a5/bzImage-f2ddafa9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7f7402...@syzkaller.appspotmail.com

BUG: spinlock bad magic on CPU#1, kworker/u4:2/29
general protection fault, probably for non-canonical address 0xdffffc00000040b6: 0000 [#1] PREEMPT SMP KASAN
KASAN: probably user-memory-access in range [0x00000000000205b0-0x00000000000205b7]
CPU: 1 PID: 29 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: btrfs-endio btrfs_end_bio_work
RIP: 0010:task_pid_nr include/linux/sched.h:1566 [inline]
RIP: 0010:spin_dump+0xc0/0x1a0 kernel/locking/spinlock_debug.c:63
Code: 41 8b 17 49 8d 46 01 48 83 f8 02 73 0f 41 b8 ff ff ff ff 49 c7 c6 a0 68 8c 8a eb 25 4d 8d be b8 05 00 00 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 af 00 00 00 49 81 c6 b0 08 00 00 45 8b
RSP: 0018:ffffc90000a5f908 EFLAGS: 00010003
RAX: 00000000000040b6 RBX: ffffc900035a77b0 RCX: 826bbd3f90acd400
RDX: 000000001ffff920 RSI: 0000000080000001 RDI: 0000000000000000
RBP: ffffc90000a5f9f0 R08: ffffc90000a5f607 R09: 1ffff9200014bec0
R10: dffffc0000000000 R11: fffff5200014bec1 R12: dffffc0000000000
R13: 0000000000000003 R14: 000000000001ffff R15: 00000000000205b7
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f302314da08 CR3: 0000000064953000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
spin_bug kernel/locking/spinlock_debug.c:77 [inline]
debug_spin_lock_before kernel/locking/spinlock_debug.c:85 [inline]
do_raw_spin_lock+0x1de/0x2f0 kernel/locking/spinlock_debug.c:114
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
_raw_spin_lock_irqsave+0xbc/0x100 kernel/locking/spinlock.c:162
__wake_up_common_lock kernel/sched/wait.c:137 [inline]
__wake_up+0x107/0x1a0 kernel/sched/wait.c:160
btrfs_encoded_read_endio+0x500/0x640 fs/btrfs/inode.c:10530
process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:task_pid_nr include/linux/sched.h:1566 [inline]
RIP: 0010:spin_dump+0xc0/0x1a0 kernel/locking/spinlock_debug.c:63
Code: 41 8b 17 49 8d 46 01 48 83 f8 02 73 0f 41 b8 ff ff ff ff 49 c7 c6 a0 68 8c 8a eb 25 4d 8d be b8 05 00 00 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 af 00 00 00 49 81 c6 b0 08 00 00 45 8b
RSP: 0018:ffffc90000a5f908 EFLAGS: 00010003
RAX: 00000000000040b6 RBX: ffffc900035a77b0 RCX: 826bbd3f90acd400
RDX: 000000001ffff920 RSI: 0000000080000001 RDI: 0000000000000000
RBP: ffffc90000a5f9f0 R08: ffffc90000a5f607 R09: 1ffff9200014bec0
R10: dffffc0000000000 R11: fffff5200014bec1 R12: dffffc0000000000
R13: 0000000000000003 R14: 000000000001ffff R15: 00000000000205b7
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f302314da08 CR3: 0000000064953000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 41 8b 17 mov (%r15),%edx
3: 49 8d 46 01 lea 0x1(%r14),%rax
7: 48 83 f8 02 cmp $0x2,%rax
b: 73 0f jae 0x1c
d: 41 b8 ff ff ff ff mov $0xffffffff,%r8d
13: 49 c7 c6 a0 68 8c 8a mov $0xffffffff8a8c68a0,%r14
1a: eb 25 jmp 0x41
1c: 4d 8d be b8 05 00 00 lea 0x5b8(%r14),%r15
23: 4c 89 f8 mov %r15,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 af 00 00 00 jne 0xe6
37: 49 81 c6 b0 08 00 00 add $0x8b0,%r14
3e: 45 rex.RB
3f: 8b .byte 0x8b


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