From: syzbot <syzbot+002fb7b2d0bc53bf7e75@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_prefill_and_lock
Date: Wed, 09 Sep 2026 21:26:32 -0700 [thread overview]
Message-ID: <6aa23178.f81106d8.2ab401.0006.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: 1fc5a74b108f Merge tag 'kmalloc_obj-v7.3-rc2' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17aeb2f9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f
dashboard link: https://syzkaller.appspot.com/bug?extid=002fb7b2d0bc53bf7e75
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/f5473bcef69a/disk-1fc5a74b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fc94ec0cede2/vmlinux-1fc5a74b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1316ecaf7adb/bzImage-1fc5a74b.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+002fb7b2d0bc53bf7e75@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.3.511/7847 is trying to acquire lock:
ffff88802c68cc60 (&pipe->mutex){+.+.}-{4:4}, at: anon_pipe_prefill_and_lock+0x16c/0x580 fs/pipe.c:165
but task is already holding lock:
ffff88807d378138 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
ffff88807d378138 (&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}:
lock_acquire kernel/locking/lockdep.c:5908 [inline]
lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5865
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
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:256
autofs_d_automount+0x490/0x950 fs/autofs/root.c:410
follow_automount fs/namei.c:1565 [inline]
__traverse_mounts+0x1b9/0x8a0 fs/namei.c:1618
traverse_mounts fs/namei.c:1647 [inline]
handle_mounts fs/namei.c:1749 [inline]
step_into_slowpath+0xb7e/0xf90 fs/namei.c:2104
step_into fs/namei.c:2152 [inline]
walk_component fs/namei.c:2288 [inline]
lookup_last fs/namei.c:2789 [inline]
path_lookupat+0x58b/0xc40 fs/namei.c:2813
filename_lookup+0x202/0x590 fs/namei.c:2842
kern_path+0x37/0x50 fs/namei.c:3036
lookup_bdev+0xd8/0x2a0 block/bdev.c:1268
resume_store+0x1d6/0x460 kernel/power/hibernate.c:1278
kobj_attr_store+0x58/0x80 lib/kobject.c:842
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&of->mutex){+.+.}-{4:4}:
lock_acquire kernel/locking/lockdep.c:5908 [inline]
lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5865
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
kernfs_fop_write_iter+0x2c2/0x5f0 fs/kernfs/file.c:336
iter_file_splice_write+0x830/0x10b0 fs/splice.c:736
do_splice_from fs/splice.c:936 [inline]
do_splice+0x109c/0x1fa0 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:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&pipe->mutex){+.+.}-{4:4}:
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3181
check_prevs_add kernel/locking/lockdep.c:3300 [inline]
validate_chain kernel/locking/lockdep.c:3924 [inline]
__lock_acquire+0x1492/0x1ec0 kernel/locking/lockdep.c:5254
lock_acquire kernel/locking/lockdep.c:5908 [inline]
lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5865
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
anon_pipe_prefill_and_lock+0x16c/0x580 fs/pipe.c:165
anon_pipe_write+0x164/0x1b50 fs/pipe.c:534
__kernel_write_iter+0x6bb/0x930 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:256
autofs_d_automount+0x490/0x950 fs/autofs/root.c:410
follow_automount fs/namei.c:1565 [inline]
__traverse_mounts+0x1b9/0x8a0 fs/namei.c:1618
traverse_mounts fs/namei.c:1647 [inline]
handle_mounts fs/namei.c:1749 [inline]
step_into_slowpath+0xb7e/0xf90 fs/namei.c:2104
step_into fs/namei.c:2152 [inline]
walk_component fs/namei.c:2288 [inline]
lookup_last fs/namei.c:2789 [inline]
path_lookupat+0x58b/0xc40 fs/namei.c:2813
filename_lookup+0x202/0x590 fs/namei.c:2842
kern_path+0x37/0x50 fs/namei.c:3036
lookup_bdev+0xd8/0x2a0 block/bdev.c:1268
resume_store+0x1d6/0x460 kernel/power/hibernate.c:1278
kobj_attr_store+0x58/0x80 lib/kobject.c:842
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
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 ***
locks held by syz.3.511/7847: 5, last CPU#0:
#0: ffff88807334f430 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
#1: ffff8880339b4460 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
#2: ffff888056438c80 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x2c2/0x5f0 fs/kernfs/file.c:336
#3: ffff888020ac5f08 (kn->active#71){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:73 [inline]
#3: ffff888020ac5f08 (kn->active#71){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x332/0x5f0 fs/kernfs/file.c:337
#4: ffff88807d378138 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
#4: ffff88807d378138 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x4f8/0xd90 fs/autofs/waitq.c:164
stack backtrace:
CPU: 0 UID: 0 PID: 7847 Comm: syz.3.511 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
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+0x178/0x1be kernel/locking/lockdep.c:2059
check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2191
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3181
check_prevs_add kernel/locking/lockdep.c:3300 [inline]
validate_chain kernel/locking/lockdep.c:3924 [inline]
__lock_acquire+0x1492/0x1ec0 kernel/locking/lockdep.c:5254
lock_acquire kernel/locking/lockdep.c:5908 [inline]
lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5865
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
anon_pipe_prefill_and_lock+0x16c/0x580 fs/pipe.c:165
anon_pipe_write+0x164/0x1b50 fs/pipe.c:534
__kernel_write_iter+0x6bb/0x930 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:256
autofs_d_automount+0x490/0x950 fs/autofs/root.c:410
follow_automount fs/namei.c:1565 [inline]
__traverse_mounts+0x1b9/0x8a0 fs/namei.c:1618
traverse_mounts fs/namei.c:1647 [inline]
handle_mounts fs/namei.c:1749 [inline]
step_into_slowpath+0xb7e/0xf90 fs/namei.c:2104
step_into fs/namei.c:2152 [inline]
walk_component fs/namei.c:2288 [inline]
lookup_last fs/namei.c:2789 [inline]
path_lookupat+0x58b/0xc40 fs/namei.c:2813
filename_lookup+0x202/0x590 fs/namei.c:2842
kern_path+0x37/0x50 fs/namei.c:3036
lookup_bdev+0xd8/0x2a0 block/bdev.c:1268
resume_store+0x1d6/0x460 kernel/power/hibernate.c:1278
kobj_attr_store+0x58/0x80 lib/kobject.c:842
sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6af/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7eff3b99e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007eff3c78c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007eff3bc25fa0 RCX: 00007eff3b99e159
RDX: 0000000000000012 RSI: 0000200000000040 RDI: 0000000000000008
RBP: 00007eff3ba35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007eff3bc26038 R14: 00007eff3bc25fa0 R15: 00007ffdcf0d0ce8
</TASK>
PM: Image not found (code -6)
---
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reply other threads:[~2026-09-10 4:26 UTC|newest]
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