syzbot


WARNING in __rt_mutex_slowlock_locked

Status: upstream: reported C repro on 2025/08/21 14:08
Subsystems: exfat ext4
[Documentation on labels]
Reported-by: syzbot+a725ab460fc1def9896f@syzkaller.appspotmail.com
First crash: 3d13h, last: 3d05h
Cause bisection: introduced by (bisect log) :
commit d2d6422f8bd17c6bb205133e290625a564194496
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri Sep 6 10:59:04 2024 +0000

  x86: Allow to enable PREEMPT_RT.

Crash: WARNING in __rt_mutex_slowlock_locked (log)
Repro: C syz .config
  
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [exfat?] [ext4?] WARNING in __rt_mutex_slowlock_locked 2 (3) 2025/08/23 00:59

Sample crash report:
exFAT-fs (loop0): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
exFAT-fs (loop0): Medium has reported failures. Some data may be lost.
exFAT-fs (loop0): failed to load upcase table (idx : 0x00010000, chksum : 0xe5674ec2, utbl_chksum : 0xe619d30d)
------------[ cut here ]------------
rtmutex deadlock detected
WARNING: CPU: 1 PID: 6147 at kernel/locking/rtmutex.c:1674 rt_mutex_handle_deadlock kernel/locking/rtmutex.c:1674 [inline]
WARNING: CPU: 1 PID: 6147 at kernel/locking/rtmutex.c:1674 __rt_mutex_slowlock kernel/locking/rtmutex.c:1734 [inline]
WARNING: CPU: 1 PID: 6147 at kernel/locking/rtmutex.c:1674 __rt_mutex_slowlock_locked+0xed2/0x25e0 kernel/locking/rtmutex.c:1760
Modules linked in:
CPU: 1 UID: 0 PID: 6147 Comm: syz.0.17 Tainted: G        W           syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:rt_mutex_handle_deadlock kernel/locking/rtmutex.c:1674 [inline]
RIP: 0010:__rt_mutex_slowlock kernel/locking/rtmutex.c:1734 [inline]
RIP: 0010:__rt_mutex_slowlock_locked+0xed2/0x25e0 kernel/locking/rtmutex.c:1760
Code: 7c 24 20 dd 4c 8b b4 24 98 00 00 00 0f 85 fd 0a 00 00 48 8b 7c 24 10 e8 2c ee 5d 09 90 48 c7 c7 00 ed 0a 8b e8 df 89 e7 ff 90 <0f> 0b 90 90 48 8b 9c 24 80 00 00 00 43 80 3c 3e 00 74 08 4c 89 e7
RSP: 0018:ffffc90003f6f840 EFLAGS: 00010246
RAX: 98a8314600ad2b00 RBX: ffff88802acb2860 RCX: ffff88802acb1dc0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003f6fa30 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed1017124863 R12: ffff88802acb34e0
R13: ffff88802acb1dd8 R14: 1ffff1100559669c R15: dffffc0000000000
FS:  0000555562c1e500(0000) GS:ffff8881269c5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000409d0000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 rt_mutex_slowlock+0xb5/0x160 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
 inode_lock_nested include/linux/fs.h:914 [inline]
 vfs_rename+0x68f/0xf00 fs/namei.c:5092
 do_renameat2+0x6ce/0xa80 fs/namei.c:5278
 __do_sys_renameat2 fs/namei.c:5312 [inline]
 __se_sys_renameat2 fs/namei.c:5309 [inline]
 __x64_sys_renameat2+0xce/0xe0 fs/namei.c:5309
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5a9fd9ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc404e6a38 EFLAGS: 00000246 ORIG_RAX: 000000000000013c
RAX: ffffffffffffffda RBX: 00007f5a9ffc5fa0 RCX: 00007f5a9fd9ebe9
RDX: 0000000000000004 RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007f5a9fe21e19 R08: 0000000000000004 R09: 0000000000000000
R10: 0000200000000140 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5a9ffc5fa0 R14: 00007f5a9ffc5fa0 R15: 0000000000000005
 </TASK>

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/21 10:00 upstream 41cd3fd15263 0b9605c8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs WARNING in __rt_mutex_slowlock_locked
2025/08/21 08:10 upstream 41cd3fd15263 0b9605c8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-upstream-fs WARNING in __rt_mutex_slowlock_locked
2025/08/21 06:29 upstream 41cd3fd15263 0b9605c8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs WARNING in __rt_mutex_slowlock_locked
2025/08/21 04:57 upstream 41cd3fd15263 0b9605c8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs WARNING in __rt_mutex_slowlock_locked
2025/08/21 03:21 upstream 41cd3fd15263 0b9605c8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs WARNING in __rt_mutex_slowlock_locked
2025/08/21 01:43 upstream 41cd3fd15263 0b9605c8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in __rt_mutex_slowlock_locked
* Struck through repros no longer work on HEAD.