From: syzbot <syzbot+459d8d87e3c2a46d4102@syzkaller.appspotmail.com>
To: autofs@vger.kernel.org, linux-kernel@vger.kernel.org,
raven@themaw.net, syzkaller-bugs@googlegroups.com
Subject: [syzbot] [autofs?] possible deadlock in anon_pipe_write (2)
Date: Fri, 17 Apr 2026 08:47:30 -0700 [thread overview]
Message-ID: <69e25612.a00a0220.1bd0ca.0005.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: 028ef9c96e96 Linux 7.0
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=147210ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a3e5e8c17cc174e
dashboard link: https://syzkaller.appspot.com/bug?extid=459d8d87e3c2a46d4102
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ec3fc4ab21e9/disk-028ef9c9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/edc0fd5a0fd3/vmlinux-028ef9c9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7c5a57bcdac7/bzImage-028ef9c9.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+459d8d87e3c2a46d4102@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz-executor/5806 is trying to acquire lock:
ffff88807ab04868 (&pipe->mutex){+.+.}-{4:4}, at: anon_pipe_write+0x163/0x1d40 fs/pipe.c:458
but task is already holding lock:
ffff888033264948 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
ffff888033264948 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x4f8/0xd90 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:614 [inline]
__mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
autofs_write fs/autofs/waitq.c:55 [inline]
autofs_notify_daemon+0x4f8/0xd90 fs/autofs/waitq.c:164
autofs_wait+0x10fd/0x1b50 fs/autofs/waitq.c:426
autofs_mount_wait+0x132/0x3b0 fs/autofs/root.c:255
autofs_d_automount+0x490/0x950 fs/autofs/root.c:409
follow_automount fs/namei.c:1560 [inline]
__traverse_mounts+0x1b9/0x8a0 fs/namei.c:1613
traverse_mounts fs/namei.c:1642 [inline]
handle_mounts fs/namei.c:1744 [inline]
step_into_slowpath+0xb7e/0xf90 fs/namei.c:2101
step_into fs/namei.c:2149 [inline]
walk_component fs/namei.c:2285 [inline]
lookup_last fs/namei.c:2786 [inline]
path_lookupat+0x58b/0xc40 fs/namei.c:2810
filename_lookup+0x202/0x590 fs/namei.c:2839
kern_path+0x37/0x50 fs/namei.c:3046
lookup_bdev+0xd8/0x280 block/bdev.c:1221
resume_store+0x1d6/0x460 kernel/power/hibernate.c:1306
kobj_attr_store+0x58/0x80 lib/kobject.c:840
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:352
aio_write+0x3ba/0x920 fs/aio.c:1633
__io_submit_one fs/aio.c:2005 [inline]
io_submit_one+0x1142/0x1fb0 fs/aio.c:2052
__do_sys_io_submit fs/aio.c:2111 [inline]
__se_sys_io_submit fs/aio.c:2081 [inline]
__x64_sys_io_submit+0x1b1/0x3a0 fs/aio.c:2081
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x106/0xf80 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:614 [inline]
__mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
kernfs_fop_write_iter+0x2c2/0x5f0 fs/kernfs/file.c:343
iter_file_splice_write+0x830/0x10a0 fs/splice.c:736
do_splice_from fs/splice.c:936 [inline]
do_splice+0x109c/0x1fd0 fs/splice.c:1349
__do_splice+0x33b/0x370 fs/splice.c:1431
__do_sys_splice fs/splice.c:1634 [inline]
__se_sys_splice fs/splice.c:1616 [inline]
__x64_sys_splice+0x187/0x250 fs/splice.c:1616
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x106/0xf80 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:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:614 [inline]
__mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
anon_pipe_write+0x163/0x1d40 fs/pipe.c:458
__kernel_write_iter+0x6b2/0x920 fs/read_write.c:621
__kernel_write+0xf6/0x140 fs/read_write.c:641
autofs_write fs/autofs/waitq.c:57 [inline]
autofs_notify_daemon+0x50d/0xd90 fs/autofs/waitq.c:164
autofs_wait+0x10fd/0x1b50 fs/autofs/waitq.c:426
autofs_mount_wait+0x132/0x3b0 fs/autofs/root.c:255
autofs_d_automount+0x490/0x950 fs/autofs/root.c:409
follow_automount fs/namei.c:1560 [inline]
__traverse_mounts+0x1b9/0x8a0 fs/namei.c:1613
traverse_mounts fs/namei.c:1642 [inline]
handle_mounts fs/namei.c:1744 [inline]
step_into_slowpath+0xb7e/0xf90 fs/namei.c:2101
step_into fs/namei.c:2149 [inline]
open_last_lookups fs/namei.c:4624 [inline]
path_openat+0xf95/0x31a0 fs/namei.c:4833
do_file_open+0x20e/0x430 fs/namei.c:4865
do_sys_openat2+0x10d/0x1e0 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x12d/0x210 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x106/0xf80 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-executor/5806:
#0: ffff888033264948 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
#0: ffff888033264948 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x4f8/0xd90 fs/autofs/waitq.c:164
stack backtrace:
CPU: 0 UID: 0 PID: 5806 Comm: syz-executor Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:614 [inline]
__mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
anon_pipe_write+0x163/0x1d40 fs/pipe.c:458
__kernel_write_iter+0x6b2/0x920 fs/read_write.c:621
__kernel_write+0xf6/0x140 fs/read_write.c:641
autofs_write fs/autofs/waitq.c:57 [inline]
autofs_notify_daemon+0x50d/0xd90 fs/autofs/waitq.c:164
autofs_wait+0x10fd/0x1b50 fs/autofs/waitq.c:426
autofs_mount_wait+0x132/0x3b0 fs/autofs/root.c:255
autofs_d_automount+0x490/0x950 fs/autofs/root.c:409
follow_automount fs/namei.c:1560 [inline]
__traverse_mounts+0x1b9/0x8a0 fs/namei.c:1613
traverse_mounts fs/namei.c:1642 [inline]
handle_mounts fs/namei.c:1744 [inline]
step_into_slowpath+0xb7e/0xf90 fs/namei.c:2101
step_into fs/namei.c:2149 [inline]
open_last_lookups fs/namei.c:4624 [inline]
path_openat+0xf95/0x31a0 fs/namei.c:4833
do_file_open+0x20e/0x430 fs/namei.c:4865
do_sys_openat2+0x10d/0x1e0 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x12d/0x210 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f757039bb3c
Code: 4c 89 54 24 18 41 89 f2 41 83 e2 40 75 40 89 f0 f7 d0 a9 00 00 41 00 74 35 89 f2 b8 01 01 00 00 48 89 fe bf 9c ff ff ff 0f 05 <48> 3d 00 f0 ff ff 77 44 48 8b 54 24 18 64 48 2b 14 25 28 00 00 00
RSP: 002b:00007ffe92381580 EFLAGS: 00000206 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f7570432048 RCX: 00007f757039bb3c
RDX: 0000000000090800 RSI: 00007ffe92382790 RDI: 00000000ffffff9c
RBP: 00007ffe92382790 R08: 00007ffe92383790 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000206 R12: 00007ffe92382790
R13: 00007f7570432048 R14: 00000000000d5761 R15: 00007ffe92384950
</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@googlegroups.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 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
reply other threads:[~2026-04-17 15:47 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=69e25612.a00a0220.1bd0ca.0005.GAE@google.com \
--to=syzbot+459d8d87e3c2a46d4102@syzkaller.appspotmail.com \
--cc=autofs@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=raven@themaw.net \
--cc=syzkaller-bugs@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.