Message-ID: <00000000000075b674061dcab0d5@google.com>
Date: Sun, 21 Jul 2024 16:57:21 -0700
From: syzbot <syzbot+0d4e0978aa13f9e1db55@...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 autofs_notify_daemon

Hello,

syzbot found the following issue on:

HEAD commit:    d7e78951a8b8 Merge tag 'net-6.11-rc0' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1642f7a5980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2602dfd9213d734c
dashboard link: https://syzkaller.appspot.com/bug?extid=0d4e0978aa13f9e1db55
compiler:       Debian clang version 15.0.6, 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/cdd2c14644df/disk-d7e78951.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7f9c9ab39b87/vmlinux-d7e78951.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1fc3658770e2/bzImage-d7e78951.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0d4e0978aa13f9e1db55@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.10.0-syzkaller-09703-gd7e78951a8b8 #0 Not tainted
------------------------------------------------------
syz.3.4748/19551 is trying to acquire lock:
ffff888059b0d940 (&sbi->pipe_mutex){+.+.}-{3:3}, at: autofs_write fs/autofs/waitq.c:55 [inline]
ffff888059b0d940 (&sbi->pipe_mutex){+.+.}-{3:3}, at: autofs_notify_daemon+0x71f/0xf80 fs/autofs/waitq.c:164

but task is already holding lock:
ffff8880758e7888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1eb/0x500 fs/kernfs/file.c:325

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&of->mutex){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       kernfs_fop_write_iter+0x1eb/0x500 fs/kernfs/file.c:325
       iter_file_splice_write+0xbd7/0x14e0 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd77/0x1900 fs/splice.c:1354
       __do_splice fs/splice.c:1436 [inline]
       __do_sys_splice fs/splice.c:1652 [inline]
       __se_sys_splice+0x331/0x4a0 fs/splice.c:1634
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&pipe->mutex){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       pipe_write+0x1c9/0x1a40 fs/pipe.c:455
       __kernel_write_iter+0x47e/0x900 fs/read_write.c:523
       __kernel_write+0x120/0x180 fs/read_write.c:543
       autofs_write fs/autofs/waitq.c:57 [inline]
       autofs_notify_daemon+0x732/0xf80 fs/autofs/waitq.c:164
       autofs_wait+0x10b8/0x1b30 fs/autofs/waitq.c:426
       autofs_do_expire_multi+0x659/0x950 fs/autofs/expire.c:590
       autofs_root_ioctl+0x4c/0x60 fs/autofs/root.c:910
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:907 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sbi->pipe_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3133 [inline]
       check_prevs_add kernel/locking/lockdep.c:3252 [inline]
       validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
       __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       autofs_write fs/autofs/waitq.c:55 [inline]
       autofs_notify_daemon+0x71f/0xf80 fs/autofs/waitq.c:164
       autofs_wait+0x10b8/0x1b30 fs/autofs/waitq.c:426
       autofs_mount_wait+0x170/0x330 fs/autofs/root.c:255
       autofs_d_automount+0x555/0x710 fs/autofs/root.c:401
       follow_automount fs/namei.c:1394 [inline]
       __traverse_mounts+0x2ba/0x580 fs/namei.c:1439
       traverse_mounts fs/namei.c:1468 [inline]
       handle_mounts fs/namei.c:1571 [inline]
       step_into+0x5e5/0x1080 fs/namei.c:1877
       lookup_last fs/namei.c:2542 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2566
       filename_lookup+0x256/0x610 fs/namei.c:2595
       kern_path+0x35/0x50 fs/namei.c:2703
       lookup_bdev+0xc5/0x290 block/bdev.c:1157
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
       kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
       iter_file_splice_write+0xbd7/0x14e0 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       direct_splice_actor+0x11e/0x220 fs/splice.c:1164
       splice_direct_to_actor+0x58e/0xc90 fs/splice.c:1108
       do_splice_direct_actor fs/splice.c:1207 [inline]
       do_splice_direct+0x28c/0x3e0 fs/splice.c:1233
       do_sendfile+0x56d/0xe20 fs/read_write.c:1295
       __do_sys_sendfile64 fs/read_write.c:1362 [inline]
       __se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

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

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

3 locks held by syz.3.4748/19551:
 #0: ffff88801e524420 (sb_writers#8){.+.+}-{0:0}, at: direct_splice_actor+0x49/0x220 fs/splice.c:1163
 #1: ffff8880758e7888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1eb/0x500 fs/kernfs/file.c:325
 #2: ffff888017adb4b8 (kn->active#65){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20f/0x500 fs/kernfs/file.c:326

stack backtrace:
CPU: 1 PID: 19551 Comm: syz.3.4748 Not tainted 6.10.0-syzkaller-09703-gd7e78951a8b8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2186
 check_prev_add kernel/locking/lockdep.c:3133 [inline]
 check_prevs_add kernel/locking/lockdep.c:3252 [inline]
 validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 autofs_write fs/autofs/waitq.c:55 [inline]
 autofs_notify_daemon+0x71f/0xf80 fs/autofs/waitq.c:164
 autofs_wait+0x10b8/0x1b30 fs/autofs/waitq.c:426
 autofs_mount_wait+0x170/0x330 fs/autofs/root.c:255
 autofs_d_automount+0x555/0x710 fs/autofs/root.c:401
 follow_automount fs/namei.c:1394 [inline]
 __traverse_mounts+0x2ba/0x580 fs/namei.c:1439
 traverse_mounts fs/namei.c:1468 [inline]
 handle_mounts fs/namei.c:1571 [inline]
 step_into+0x5e5/0x1080 fs/namei.c:1877
 lookup_last fs/namei.c:2542 [inline]
 path_lookupat+0x16f/0x450 fs/namei.c:2566
 filename_lookup+0x256/0x610 fs/namei.c:2595
 kern_path+0x35/0x50 fs/namei.c:2703
 lookup_bdev+0xc5/0x290 block/bdev.c:1157
 resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
 kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
 iter_file_splice_write+0xbd7/0x14e0 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0x11e/0x220 fs/splice.c:1164
 splice_direct_to_actor+0x58e/0xc90 fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0x28c/0x3e0 fs/splice.c:1233
 do_sendfile+0x56d/0xe20 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f75ec575b59
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:00007f75ebfde048 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f75ec706038 RCX: 00007f75ec575b59
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
RBP: 00007f75ec5e4e5d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f75ec706038 R15: 00007ffef2866ed8
 </TASK>
PM: Image not found (code -6)


---
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