Message-ID: <000000000000931657061ffc8ad9@google.com>
Date: Sun, 18 Aug 2024 15:16:17 -0700
From: syzbot <syzbot+b4567a8b2d2ad5f9dd06@...kaller.appspotmail.com>
To: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com, tj@...nel.org
Subject: [syzbot] [kernfs?] possible deadlock in walk_component (4)

Hello,

syzbot found the following issue on:

HEAD commit:    6b0f8db921ab Merge tag 'execve-v6.11-rc4' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16766c05980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=54e9d4be0c7a0d11
dashboard link: https://syzkaller.appspot.com/bug?extid=b4567a8b2d2ad5f9dd06
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 (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-6b0f8db9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5829b92d3000/vmlinux-6b0f8db9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0b382f2bc118/bzImage-6b0f8db9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b4567a8b2d2ad5f9dd06@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.11.0-rc3-syzkaller-00013-g6b0f8db921ab #0 Not tainted
------------------------------------------------------
syz.0.2542/15091 is trying to acquire lock:
ffff888047e58cf8 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:809 [inline]
ffff888047e58cf8 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_slow fs/namei.c:1734 [inline]
ffff888047e58cf8 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: walk_component+0x342/0x5b0 fs/namei.c:2039

but task is already holding lock:
ffff8880484c6488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x281/0x500 fs/kernfs/file.c:325

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&of->mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       kernfs_fop_write_iter+0x281/0x500 fs/kernfs/file.c:325
       iter_file_splice_write+0x906/0x10b0 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0x148c/0x1f90 fs/splice.c:1354
       __do_splice+0x327/0x360 fs/splice.c:1436
       __do_sys_splice fs/splice.c:1652 [inline]
       __se_sys_splice fs/splice.c:1634 [inline]
       __x64_sys_splice+0x1d2/0x260 fs/splice.c:1634
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&pipe->mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       pipe_lock fs/pipe.c:92 [inline]
       pipe_lock+0x64/0x80 fs/pipe.c:89
       iter_file_splice_write+0x1f0/0x10b0 fs/splice.c:687
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0x148c/0x1f90 fs/splice.c:1354
       __do_splice+0x327/0x360 fs/splice.c:1436
       __do_sys_splice fs/splice.c:1652 [inline]
       __se_sys_splice fs/splice.c:1634 [inline]
       __x64_sys_splice+0x1d2/0x260 fs/splice.c:1634
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (sb_writers#6){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1675 [inline]
       sb_start_write include/linux/fs.h:1811 [inline]
       mnt_want_write+0x6f/0x450 fs/namespace.c:515
       ovl_create_object+0x12e/0x300 fs/overlayfs/dir.c:642
       lookup_open.isra.0+0x10a1/0x13c0 fs/namei.c:3578
       open_last_lookups fs/namei.c:3647 [inline]
       path_openat+0xa3b/0x2d20 fs/namei.c:3883
       do_filp_open+0x1dc/0x430 fs/namei.c:3913
       do_sys_openat2+0x17a/0x1e0 fs/open.c:1416
       do_sys_open fs/open.c:1431 [inline]
       __do_sys_openat fs/open.c:1447 [inline]
       __se_sys_openat fs/open.c:1442 [inline]
       __x64_sys_openat+0x175/0x210 fs/open.c:1442
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3133 [inline]
       check_prevs_add kernel/locking/lockdep.c:3252 [inline]
       validate_chain kernel/locking/lockdep.c:3868 [inline]
       __lock_acquire+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
       lock_acquire kernel/locking/lockdep.c:5759 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
       down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
       inode_lock_shared include/linux/fs.h:809 [inline]
       lookup_slow fs/namei.c:1734 [inline]
       walk_component+0x342/0x5b0 fs/namei.c:2039
       lookup_last fs/namei.c:2542 [inline]
       path_lookupat+0x17f/0x770 fs/namei.c:2566
       filename_lookup+0x1e5/0x5b0 fs/namei.c:2595
       kern_path+0x35/0x50 fs/namei.c:2703
       lookup_bdev+0xd9/0x280 block/bdev.c:1157
       resume_store+0x1d8/0x460 kernel/power/hibernate.c:1235
       kobj_attr_store+0x55/0x80 lib/kobject.c:840
       sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:136
       kernfs_fop_write_iter+0x343/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:497 [inline]
       vfs_write+0x6b6/0x1140 fs/read_write.c:590
       ksys_write+0x12f/0x260 fs/read_write.c:643
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &ovl_i_mutex_dir_key[depth] --> &pipe->mutex --> &of->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&of->mutex);
                               lock(&pipe->mutex);
                               lock(&of->mutex);
  rlock(&ovl_i_mutex_dir_key[depth]);

 *** DEADLOCK ***

4 locks held by syz.0.2542/15091:
 #0: ffff8880298c19c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xeb/0x180 fs/file.c:1187
 #1: ffff888024928420 (sb_writers#9){.+.+}-{0:0}, at: ksys_write+0x12f/0x260 fs/read_write.c:643
 #2: ffff8880484c6488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x281/0x500 fs/kernfs/file.c:325
 #3: ffff888016744698 (kn->active#77){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2a4/0x500 fs/kernfs/file.c:326

stack backtrace:
CPU: 1 UID: 0 PID: 15091 Comm: syz.0.2542 Not tainted 6.11.0-rc3-syzkaller-00013-g6b0f8db921ab #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
 check_noncircular+0x31a/0x400 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 kernel/locking/lockdep.c:3868 [inline]
 __lock_acquire+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
 lock_acquire kernel/locking/lockdep.c:5759 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
 down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
 inode_lock_shared include/linux/fs.h:809 [inline]
 lookup_slow fs/namei.c:1734 [inline]
 walk_component+0x342/0x5b0 fs/namei.c:2039
 lookup_last fs/namei.c:2542 [inline]
 path_lookupat+0x17f/0x770 fs/namei.c:2566
 filename_lookup+0x1e5/0x5b0 fs/namei.c:2595
 kern_path+0x35/0x50 fs/namei.c:2703
 lookup_bdev+0xd9/0x280 block/bdev.c:1157
 resume_store+0x1d8/0x460 kernel/power/hibernate.c:1235
 kobj_attr_store+0x55/0x80 lib/kobject.c:840
 sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x343/0x500 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x6b6/0x1140 fs/read_write.c:590
 ksys_write+0x12f/0x260 fs/read_write.c:643
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7efcd1f799f9
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:00007efcd2d56038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007efcd2115f80 RCX: 00007efcd1f799f9
RDX: 0000000000000012 RSI: 0000000020000140 RDI: 0000000000000009
RBP: 00007efcd1fe78ee R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007efcd2115f80 R15: 00007ffdbb59c4e8
 </TASK>
PM: Image not found (code -6)


---
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