syzbot


possible deadlock in kernfs_fop_write_iter

Status: upstream: reported on 2024/07/01 22:38
Subsystems: kernfs
[Documentation on labels]
Reported-by: syzbot+24386307cce6239b5f68@syzkaller.appspotmail.com
First crash: 15d, last: 15d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [kernfs?] possible deadlock in kernfs_fop_write_iter 0 (1) 2024/07/01 22:38

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.10.0-rc5-syzkaller-00155-g66e55ff12e73 #0 Not tainted
------------------------------------------------------
syz.2.1818/11922 is trying to acquire lock:
ffff88803d074c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x281/0x500 fs/kernfs/file.c:325

but task is already holding lock:
ffff88802d7a3868 (&pipe->mutex){+.+.}-{3:3}, at: pipe_lock fs/pipe.c:92 [inline]
ffff88802d7a3868 (&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+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

-> #2 (sb_writers#5){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1655 [inline]
       sb_start_write include/linux/fs.h:1791 [inline]
       mnt_want_write+0x6f/0x450 fs/namespace.c:409
       ovl_set_or_remove_acl fs/overlayfs/inode.c:517 [inline]
       ovl_set_acl+0x518/0xa00 fs/overlayfs/inode.c:566
       set_posix_acl+0x25c/0x320 fs/posix_acl.c:955
       vfs_set_acl+0x53d/0x940 fs/posix_acl.c:1134
       do_set_acl+0x15a/0x1b0 fs/posix_acl.c:1279
       do_setxattr+0xeb/0x170 fs/xattr.c:626
       setxattr+0x15d/0x180 fs/xattr.c:652
       path_setxattr+0x179/0x1e0 fs/xattr.c:671
       __do_sys_lsetxattr fs/xattr.c:694 [inline]
       __se_sys_lsetxattr fs/xattr.c:690 [inline]
       __x64_sys_lsetxattr+0xc1/0x160 fs/xattr.c:690
       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]#2){++++}-{3:3}:
       down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
       inode_lock_shared include/linux/fs.h:801 [inline]
       lookup_slow fs/namei.c:1708 [inline]
       walk_component+0x342/0x5b0 fs/namei.c:2004
       lookup_last fs/namei.c:2469 [inline]
       path_lookupat+0x17f/0x770 fs/namei.c:2493
       filename_lookup+0x1e5/0x5b0 fs/namei.c:2522
       kern_path+0x35/0x50 fs/namei.c:2630
       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

-> #0 (&of->mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
       lock_acquire kernel/locking/lockdep.c:5754 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
       __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

other info that might help us debug this:

Chain exists of:
  &of->mutex --> sb_writers#5 --> &pipe->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pipe->mutex);
                               lock(sb_writers#5);
                               lock(&pipe->mutex);
  lock(&of->mutex);

 *** DEADLOCK ***

2 locks held by syz.2.1818/11922:
 #0: ffff888024784420 (sb_writers#9){.+.+}-{0:0}, at: __do_splice+0x327/0x360 fs/splice.c:1436
 #1: ffff88802d7a3868 (&pipe->mutex){+.+.}-{3:3}, at: pipe_lock fs/pipe.c:92 [inline]
 #1: ffff88802d7a3868 (&pipe->mutex){+.+.}-{3:3}, at: pipe_lock+0x64/0x80 fs/pipe.c:89

stack backtrace:
CPU: 2 PID: 11922 Comm: syz.2.1818 Not tainted 6.10.0-rc5-syzkaller-00155-g66e55ff12e73 #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:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
 lock_acquire kernel/locking/lockdep.c:5754 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
 __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
RIP: 0033:0x7f5821175b29
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:00007f5821e78048 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f5821304070 RCX: 00007f5821175b29
RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f58211f6756 R08: 000000000000bfd1 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f5821304070 R15: 00007ffda6f8dbe8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/06/27 22:27 upstream 66e55ff12e73 6ef39602 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in kernfs_fop_write_iter
* Struck through repros no longer work on HEAD.