linux-kernel - Re: [syzbot] [block?] general protection fault in rtlock_slowlock

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Message-ID: <6911e7eb.a70a0220.22f260.00f2.GAE@google.com>
Date: Mon, 10 Nov 2025 05:26:03 -0800
From: syzbot <syzbot+08df3e4c9b304b37cb04@...kaller.appspotmail.com>
To: eadavis@...com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [block?] general protection fault in rtlock_slowlock_locked

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: bad unlock balance in lbmIOWait

loop1: detected capacity change from 0 to 32768
=====================================
WARNING: bad unlock balance detected!
syzkaller #0 Not tainted
-------------------------------------
syz.1.18/6461 is trying to release lock (jfsLCacheLock) at:
[<ffffffff833d0e04>] spin_unlock_irqrestore include/linux/spinlock_rt.h:122 [inline]
[<ffffffff833d0e04>] lbmIOWait+0x1d4/0x610 fs/jfs/jfs_logmgr.c:2150
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz.1.18/6461:
 #0: ffff888027e480d0 (&type->s_umount_key#53/1){+.+.}-{4:4}, at: alloc_super+0x1ba/0x9a0 fs/super.c:344

stack backtrace:
CPU: 1 UID: 0 PID: 6461 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_unlock_imbalance_bug+0xdc/0xf0 kernel/locking/lockdep.c:5298
 __lock_release kernel/locking/lockdep.c:5537 [inline]
 lock_release+0x269/0x3e0 kernel/locking/lockdep.c:5889
 rt_spin_unlock+0x29/0x200 kernel/locking/spinlock_rt.c:80
 spin_unlock_irqrestore include/linux/spinlock_rt.h:122 [inline]
 lbmIOWait+0x1d4/0x610 fs/jfs/jfs_logmgr.c:2150
 lmLogInit+0xeb1/0x1a00 fs/jfs/jfs_logmgr.c:1372
 open_inline_log fs/jfs/jfs_logmgr.c:1175 [inline]
 lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1069
 jfs_mount_rw+0xe9/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
 vfs_get_tree+0x92/0x2b0 fs/super.c:1751
 fc_mount fs/namespace.c:1208 [inline]
 do_new_mount_fc fs/namespace.c:3651 [inline]
 do_new_mount+0x302/0xa10 fs/namespace.c:3727
 do_mount fs/namespace.c:4050 [inline]
 __do_sys_mount fs/namespace.c:4238 [inline]
 __se_sys_mount+0x313/0x410 fs/namespace.c:4215
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0b7cee0e6a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0b7c545e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f0b7c545ef0 RCX: 00007f0b7cee0e6a
RDX: 0000200000000400 RSI: 0000200000000380 RDI: 00007f0b7c545eb0
RBP: 0000200000000400 R08: 00007f0b7c545ef0 R09: 000000000001c802
R10: 000000000001c802 R11: 0000000000000246 R12: 0000200000000380
R13: 00007f0b7c545eb0 R14: 0000000000005f74 R15: 0000200000002740
 </TASK>
------------[ cut here ]------------
WARNING: CPU: 1 PID: 6461 at ./include/linux/sched.h:2353 __migrate_enable include/linux/sched.h:2353 [inline]
WARNING: CPU: 1 PID: 6461 at ./include/linux/sched.h:2353 migrate_enable include/linux/sched.h:2417 [inline]
WARNING: CPU: 1 PID: 6461 at ./include/linux/sched.h:2353 rt_spin_unlock+0x174/0x200 kernel/locking/spinlock_rt.c:81
Modules linked in:
CPU: 1 UID: 0 PID: 6461 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__migrate_enable include/linux/sched.h:2353 [inline]
RIP: 0010:migrate_enable include/linux/sched.h:2417 [inline]
RIP: 0010:rt_spin_unlock+0x174/0x200 kernel/locking/spinlock_rt.c:81
Code: 8d 35 00 00 00 00 48 c7 c7 40 a8 5a 8d e8 e4 36 d9 f6 e8 af f1 e2 f6 48 89 df 5b 41 5c 41 5d 41 5e 41 5f 5d e9 9d 00 00 00 90 <0f> 0b 90 eb 8d e8 32 4c cd f6 e9 1b ff ff ff 44 89 f1 80 e1 07 fe
RSP: 0018:ffffc900041f7708 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff8d9dfb40 RCX: ecc696ffabe70d00
RDX: 0000000000000000 RSI: ffffffff8cf64ad6 RDI: ffffffff8b3ddd60
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1a90bc0 R12: 1ffff11004a2e090
R13: ffff888025170000 R14: ffff888025170480 R15: dffffc0000000000
FS:  00007f0b7c5466c0(0000) GS:ffff888126ef7000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f51a5c94000 CR3: 000000005514c000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 spin_unlock_irqrestore include/linux/spinlock_rt.h:122 [inline]
 lbmIOWait+0x1d4/0x610 fs/jfs/jfs_logmgr.c:2150
 lmLogInit+0xeb1/0x1a00 fs/jfs/jfs_logmgr.c:1372
 open_inline_log fs/jfs/jfs_logmgr.c:1175 [inline]
 lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1069
 jfs_mount_rw+0xe9/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
 vfs_get_tree+0x92/0x2b0 fs/super.c:1751
 fc_mount fs/namespace.c:1208 [inline]
 do_new_mount_fc fs/namespace.c:3651 [inline]
 do_new_mount+0x302/0xa10 fs/namespace.c:3727
 do_mount fs/namespace.c:4050 [inline]
 __do_sys_mount fs/namespace.c:4238 [inline]
 __se_sys_mount+0x313/0x410 fs/namespace.c:4215
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0b7cee0e6a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0b7c545e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f0b7c545ef0 RCX: 00007f0b7cee0e6a
RDX: 0000200000000400 RSI: 0000200000000380 RDI: 00007f0b7c545eb0
RBP: 0000200000000400 R08: 00007f0b7c545ef0 R09: 000000000001c802
R10: 000000000001c802 R11: 0000000000000246 R12: 0000200000000380
R13: 00007f0b7c545eb0 R14: 0000000000005f74 R15: 0000200000002740
 </TASK>


Tested on:

commit:         e9a6fb0b Linux 6.18-rc5
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=134a30b4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=41ad820f608cb833
dashboard link: https://syzkaller.appspot.com/bug?extid=08df3e4c9b304b37cb04
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13a4b412580000