Message-ID: <CAKYAXd86eFyX5sVi_5exaFJ-wGn2U16n_L1c9ouDBnFGPuH_qg@mail.gmail.com>
Date: Wed, 12 Nov 2025 12:37:03 +0900
From: Namjae Jeon <linkinjeon@...nel.org>
To: syzbot <syzbot+5216036fc59c43d1ee02@...kaller.appspotmail.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	sj1557.seo@...sung.com, syzkaller-bugs@...glegroups.com, 
	"Yuezhang.Mo" <Yuezhang.Mo@...y.com>
Subject: Re: [syzbot] [exfat?] WARNING in __rt_mutex_slowlock_locked (2)

#syz test

On Fri, Nov 7, 2025 at 8:14 AM syzbot
<syzbot+5216036fc59c43d1ee02@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    c2c2ccfd4ba7 Merge tag 'net-6.18-rc5' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=151be114580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=41ad820f608cb833
> dashboard link: https://syzkaller.appspot.com/bug?extid=5216036fc59c43d1ee02
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11062a58580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16e19084580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/121c46acc3df/disk-c2c2ccfd.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/eb0aef8fb7a1/vmlinux-c2c2ccfd.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a2bba0757aa5/bzImage-c2c2ccfd.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/03760a9baabf/mount_0.gz
>   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12084532580000)
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5216036fc59c43d1ee02@...kaller.appspotmail.com
>
> loop0: detected capacity change from 0 to 256
> exFAT-fs (loop0): start_clu is invalid cluster(0x400)
> ------------[ cut here ]------------
> rtmutex deadlock detected
> WARNING: CPU: 0 PID: 6071 at kernel/locking/rtmutex.c:1674 rt_mutex_handle_deadlock kernel/locking/rtmutex.c:1674 [inline]
> WARNING: CPU: 0 PID: 6071 at kernel/locking/rtmutex.c:1674 __rt_mutex_slowlock kernel/locking/rtmutex.c:1734 [inline]
> WARNING: CPU: 0 PID: 6071 at kernel/locking/rtmutex.c:1674 __rt_mutex_slowlock_locked+0xed2/0x25e0 kernel/locking/rtmutex.c:1760
> Modules linked in:
> CPU: 0 UID: 0 PID: 6071 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
> 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 4c 50 28 09 90 48 c7 c7 60 fd ea 8a e8 ef 62 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:ffffc90003d87a20 EFLAGS: 00010246
> RAX: 5bae39e042a2bb00 RBX: ffff88802472e4e0 RCX: ffff88802472da00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc90003d87c10 R08: 0000000000000000 R09: 0000000000000000
> R10: dffffc0000000000 R11: ffffed101710487b R12: ffff88802472f160
> R13: ffff88802472da18 R14: 1ffff110048e5e2c R15: dffffc0000000000
> FS:  00005555931b8500(0000) GS:ffff888126df9000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffefdd79178 CR3: 000000003e14c000 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 include/linux/fs.h:980 [inline]
>  vfs_rmdir+0xf7/0x520 fs/namei.c:4537
>  do_rmdir+0x25f/0x550 fs/namei.c:4603
>  __do_sys_unlinkat fs/namei.c:4777 [inline]
>  __se_sys_unlinkat fs/namei.c:4771 [inline]
>  __x64_sys_unlinkat+0xc2/0xf0 fs/namei.c:4771
>  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: 0033:0x7f03a63ff6c9
> 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:00007ffd1d6ca228 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
> RAX: ffffffffffffffda RBX: 00007f03a6655fa0 RCX: 00007f03a63ff6c9
> RDX: 0000000000000200 RSI: 0000200000000040 RDI: 0000000000000006
> RBP: 00007f03a6481f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007f03a6655fa0 R14: 00007f03a6655fa0 R15: 0000000000000003
>  </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup

View attachment "0001-exfat-validate-the-cluster-bitmap-bits-of-directory.patch" of type "text/x-patch" (6088 bytes)

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