Message-ID: <681dd491.050a0220.a19a9.012b.GAE@google.com>
Date: Fri, 09 May 2025 03:10:25 -0700
From: syzbot <syzbot+247d7a192c296bf9769c@...kaller.appspotmail.com>
To: autofs@...r.kernel.org, linux-kernel@...r.kernel.org, raven@...maw.net, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [autofs?] possible deadlock in anon_pipe_write

Hello,

syzbot found the following issue on:

HEAD commit:    0d8d44db295c Merge tag 'for-6.15-rc5-tag' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1236fb68580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b39cb28b0a399ed3
dashboard link: https://syzkaller.appspot.com/bug?extid=247d7a192c296bf9769c
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5536cda9f25f/disk-0d8d44db.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/92d52f7afb23/vmlinux-0d8d44db.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a31f0b2e7b87/bzImage-0d8d44db.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+247d7a192c296bf9769c@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc5-syzkaller-00032-g0d8d44db295c #0 Not tainted
------------------------------------------------------
syz.4.1562/14048 is trying to acquire lock:
ffff88807af9fc68 (&pipe->mutex){+.+.}-{4:4}, at: anon_pipe_write+0x15d/0x1a70 fs/pipe.c:459

but task is already holding lock:
ffff8880588b8140 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
ffff8880588b8140 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x4a6/0xd60 fs/autofs/waitq.c:164

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sbi->pipe_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       autofs_write fs/autofs/waitq.c:55 [inline]
       autofs_notify_daemon+0x4a6/0xd60 fs/autofs/waitq.c:164
       autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426
       autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255
       autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401
       follow_automount fs/namei.c:1455 [inline]
       __traverse_mounts+0x192/0x790 fs/namei.c:1500
       traverse_mounts fs/namei.c:1529 [inline]
       handle_mounts fs/namei.c:1632 [inline]
       step_into+0x5aa/0x2270 fs/namei.c:1976
       walk_component+0xfc/0x5b0 fs/namei.c:2144
       lookup_last fs/namei.c:2636 [inline]
       path_lookupat+0x17e/0x780 fs/namei.c:2660
       filename_lookup+0x224/0x5f0 fs/namei.c:2689
       kern_path+0x35/0x50 fs/namei.c:2822
       lookup_bdev+0xd8/0x280 block/bdev.c:1205
       resume_store+0x1d6/0x460 kernel/power/hibernate.c:1248
       kobj_attr_store+0x55/0x80 lib/kobject.c:840
       sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:591 [inline]
       vfs_write+0x5ba/0x1180 fs/read_write.c:684
       ksys_write+0x12a/0x240 fs/read_write.c:736
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&of->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325
       iter_file_splice_write+0x91c/0x1150 fs/splice.c:738
       do_splice_from fs/splice.c:935 [inline]
       do_splice+0x1475/0x1fc0 fs/splice.c:1348
       __do_splice+0x32a/0x360 fs/splice.c:1430
       __do_sys_splice fs/splice.c:1633 [inline]
       __se_sys_splice fs/splice.c:1615 [inline]
       __x64_sys_splice+0x187/0x250 fs/splice.c:1615
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&pipe->mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain kernel/locking/lockdep.c:3909 [inline]
       __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
       lock_acquire kernel/locking/lockdep.c:5866 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       anon_pipe_write+0x15d/0x1a70 fs/pipe.c:459
       __kernel_write_iter+0x71d/0xa90 fs/read_write.c:617
       __kernel_write+0xf5/0x140 fs/read_write.c:637
       autofs_write fs/autofs/waitq.c:57 [inline]
       autofs_notify_daemon+0x4db/0xd60 fs/autofs/waitq.c:164
       autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426
       autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255
       autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401
       follow_automount fs/namei.c:1455 [inline]
       __traverse_mounts+0x192/0x790 fs/namei.c:1500
       traverse_mounts fs/namei.c:1529 [inline]
       handle_mounts fs/namei.c:1632 [inline]
       step_into+0x5aa/0x2270 fs/namei.c:1976
       walk_component+0xfc/0x5b0 fs/namei.c:2144
       lookup_last fs/namei.c:2636 [inline]
       path_lookupat+0x17e/0x780 fs/namei.c:2660
       filename_lookup+0x224/0x5f0 fs/namei.c:2689
       user_path_at+0x3a/0x60 fs/namei.c:3120
       do_mount fs/namespace.c:4221 [inline]
       __do_sys_mount fs/namespace.c:4435 [inline]
       __se_sys_mount fs/namespace.c:4412 [inline]
       __x64_sys_mount+0x1fc/0x310 fs/namespace.c:4412
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &pipe->mutex --> &of->mutex --> &sbi->pipe_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->pipe_mutex);
                               lock(&of->mutex);
                               lock(&sbi->pipe_mutex);
  lock(&pipe->mutex);

 *** DEADLOCK ***

1 lock held by syz.4.1562/14048:
 #0: ffff8880588b8140 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
 #0: ffff8880588b8140 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x4a6/0xd60 fs/autofs/waitq.c:164

stack backtrace:
CPU: 1 UID: 0 PID: 14048 Comm: syz.4.1562 Not tainted 6.15.0-rc5-syzkaller-00032-g0d8d44db295c #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2079
 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain kernel/locking/lockdep.c:3909 [inline]
 __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
 lock_acquire kernel/locking/lockdep.c:5866 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
 anon_pipe_write+0x15d/0x1a70 fs/pipe.c:459
 __kernel_write_iter+0x71d/0xa90 fs/read_write.c:617
 __kernel_write+0xf5/0x140 fs/read_write.c:637
 autofs_write fs/autofs/waitq.c:57 [inline]
 autofs_notify_daemon+0x4db/0xd60 fs/autofs/waitq.c:164
 autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426
 autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255
 autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401
 follow_automount fs/namei.c:1455 [inline]
 __traverse_mounts+0x192/0x790 fs/namei.c:1500
 traverse_mounts fs/namei.c:1529 [inline]
 handle_mounts fs/namei.c:1632 [inline]
 step_into+0x5aa/0x2270 fs/namei.c:1976
 walk_component+0xfc/0x5b0 fs/namei.c:2144
 lookup_last fs/namei.c:2636 [inline]
 path_lookupat+0x17e/0x780 fs/namei.c:2660
 filename_lookup+0x224/0x5f0 fs/namei.c:2689
 user_path_at+0x3a/0x60 fs/namei.c:3120
 do_mount fs/namespace.c:4221 [inline]
 __do_sys_mount fs/namespace.c:4435 [inline]
 __se_sys_mount fs/namespace.c:4412 [inline]
 __x64_sys_mount+0x1fc/0x310 fs/namespace.c:4412
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7faef658e969
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:00007faef7347038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007faef67b5fa0 RCX: 00007faef658e969
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000000
RBP: 00007faef6610ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000010000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007faef67b5fa0 R15: 00007ffeefd9fb38
 </TASK>


---
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