Message-ID: <670cc0d3.050a0220.4cbc0.0046.GAE@google.com>
Date: Sun, 13 Oct 2024 23:57:23 -0700
From: syzbot <syzbot+1cfd86253864f61b533e@...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 kernfs_fop_write_iter (2)

Hello,

syzbot found the following issue on:

HEAD commit:    b983b271662b misc: sgi-gru: Don't disable preemption in GR..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17d53780580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fb6ea01107fa96bd
dashboard link: https://syzkaller.appspot.com/bug?extid=1cfd86253864f61b533e
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/7feb34a89c2a/non_bootable_disk-b983b271.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a81cb8020fb3/vmlinux-b983b271.xz
kernel image: https://storage.googleapis.com/syzbot-assets/912e503e8fb2/bzImage-b983b271.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1cfd86253864f61b533e@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc2-syzkaller-00061-gb983b271662b #0 Not tainted
------------------------------------------------------
syz.1.1735/11566 is trying to acquire lock:
ffff8880336f9088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x27b/0x500 fs/kernfs/file.c:325

but task is already holding lock:
ffff888027fa3868 (&pipe->mutex){+.+.}-{3:3}, at: pipe_lock fs/pipe.c:92 [inline]
ffff888027fa3868 (&pipe->mutex){+.+.}-{3:3}, at: pipe_lock+0x64/0x80 fs/pipe.c:89

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&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+0x1eb/0x10b0 fs/splice.c:687
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0x145c/0x1f60 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+0x1cd/0x270 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 (sb_writers#6){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1716 [inline]
       sb_start_write include/linux/fs.h:1852 [inline]
       mnt_want_write+0x6f/0x450 fs/namespace.c:515
       ovl_create_object+0x12e/0x300 fs/overlayfs/dir.c:642
       lookup_open.isra.0+0x1174/0x14c0 fs/namei.c:3595
       open_last_lookups fs/namei.c:3694 [inline]
       path_openat+0x904/0x2d60 fs/namei.c:3930
       do_filp_open+0x1dc/0x430 fs/namei.c:3960
       do_sys_openat2+0x17a/0x1e0 fs/open.c:1415
       do_sys_open fs/open.c:1430 [inline]
       __do_sys_creat fs/open.c:1506 [inline]
       __se_sys_creat fs/open.c:1500 [inline]
       __x64_sys_creat+0xcd/0x120 fs/open.c:1500
       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 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
       down_read+0x9a/0x330 kernel/locking/rwsem.c:1524
       inode_lock_shared include/linux/fs.h:825 [inline]
       lookup_slow fs/namei.c:1748 [inline]
       walk_component+0x342/0x5b0 fs/namei.c:2053
       lookup_last fs/namei.c:2556 [inline]
       path_lookupat+0x17f/0x770 fs/namei.c:2580
       filename_lookup+0x1e5/0x5b0 fs/namei.c:2609
       kern_path+0x35/0x50 fs/namei.c:2717
       lookup_bdev+0xd9/0x280 block/bdev.c:1164
       resume_store+0x1d8/0x460 kernel/power/hibernate.c:1239
       kobj_attr_store+0x55/0x80 lib/kobject.c:840
       sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:136
       kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:590 [inline]
       vfs_write+0x6b5/0x1140 fs/read_write.c:683
       ksys_write+0x12f/0x260 fs/read_write.c:736
       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 (&of->mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain kernel/locking/lockdep.c:3904 [inline]
       __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202
       lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       kernfs_fop_write_iter+0x27b/0x500 fs/kernfs/file.c:325
       iter_file_splice_write+0x90f/0x10b0 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0x145c/0x1f60 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+0x1cd/0x270 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

other info that might help us debug this:

Chain exists of:
  &of->mutex --> sb_writers#6 --> &pipe->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pipe->mutex);
                               lock(sb_writers#6);
                               lock(&pipe->mutex);
  lock(&of->mutex);

 *** DEADLOCK ***

2 locks held by syz.1.1735/11566:
 #0: ffff888029218420 (sb_writers#9){.+.+}-{0:0}, at: __do_splice+0x327/0x360 fs/splice.c:1436
 #1: ffff888027fa3868 (&pipe->mutex){+.+.}-{3:3}, at: pipe_lock fs/pipe.c:92 [inline]
 #1: ffff888027fa3868 (&pipe->mutex){+.+.}-{3:3}, at: pipe_lock+0x64/0x80 fs/pipe.c:89

stack backtrace:
CPU: 3 UID: 0 PID: 11566 Comm: syz.1.1735 Not tainted 6.12.0-rc2-syzkaller-00061-gb983b271662b #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:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x41c/0x610 kernel/locking/lockdep.c:2074
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain kernel/locking/lockdep.c:3904 [inline]
 __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5202
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
 kernfs_fop_write_iter+0x27b/0x500 fs/kernfs/file.c:325
 iter_file_splice_write+0x90f/0x10b0 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 do_splice+0x145c/0x1f60 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+0x1cd/0x270 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
RIP: 0033:0x7f2d5977dff9
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:00007f2d5a4c5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f2d59936058 RCX: 00007f2d5977dff9
RDX: 000000000000000f RSI: 0000000000000000 RDI: 000000000000000d
RBP: 00007f2d597f0296 R08: 000000000000bfd1 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f2d59936058 R15: 00007ffebf2e0bd8
 </TASK>


---
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