From: syzbot <syzbot+4c493dcd5a68168a94b2@syzkaller.appspotmail.com>
To: gregkh@linuxfoundation.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
tj@kernel.org
Subject: Re: [syzbot] [kernfs?] possible deadlock in kernfs_seq_start
Date: Tue, 07 May 2024 22:36:18 -0700 [thread overview]
Message-ID: <00000000000091228c0617eaae32@google.com> (raw)
In-Reply-To: <0000000000006399c80617120daa@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: dccb07f2914c Merge tag 'for-6.9-rc7-tag' of git://git.kern..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=137daa6c980000
kernel config: https://syzkaller.appspot.com/x/.config?x=9d7ea7de0cb32587
dashboard link: https://syzkaller.appspot.com/bug?extid=4c493dcd5a68168a94b2
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1134f3c0980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1367a504980000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ea1961ce01fe/disk-dccb07f2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/445a00347402/vmlinux-dccb07f2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/461aed7c4df3/bzImage-dccb07f2.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4c493dcd5a68168a94b2@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc7-syzkaller-00012-gdccb07f2914c #0 Not tainted
------------------------------------------------------
syz-executor149/5078 is trying to acquire lock:
ffff88802a978888 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154
but task is already holding lock:
ffff88802d80b540 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #4 (&p->lock){+.+.}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
call_read_iter include/linux/fs.h:2104 [inline]
copy_splice_read+0x662/0xb60 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
do_sendfile+0x515/0xdc0 fs/read_write.c:1301
__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+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #3 (&pipe->mutex){+.+.}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
iter_file_splice_write+0x335/0x14e0 fs/splice.c:687
backing_file_splice_write+0x2bc/0x4c0 fs/backing-file.c:289
ovl_splice_write+0x3cf/0x500 fs/overlayfs/file.c:379
do_splice_from fs/splice.c:941 [inline]
do_splice+0xd77/0x1880 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+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #2 (sb_writers#4){.+.+}-{0:0}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1664 [inline]
sb_start_write+0x4d/0x1c0 include/linux/fs.h:1800
mnt_want_write+0x3f/0x90 fs/namespace.c:409
ovl_create_object+0x13b/0x370 fs/overlayfs/dir.c:629
lookup_open fs/namei.c:3497 [inline]
open_last_lookups fs/namei.c:3566 [inline]
path_openat+0x1425/0x3240 fs/namei.c:3796
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_open fs/open.c:1429 [inline]
__se_sys_open fs/open.c:1425 [inline]
__x64_sys_open+0x225/0x270 fs/open.c:1425
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
inode_lock_shared include/linux/fs.h:805 [inline]
lookup_slow+0x45/0x70 fs/namei.c:1708
walk_component+0x2e1/0x410 fs/namei.c:2004
lookup_last fs/namei.c:2461 [inline]
path_lookupat+0x16f/0x450 fs/namei.c:2485
filename_lookup+0x256/0x610 fs/namei.c:2514
kern_path+0x35/0x50 fs/namei.c:2622
lookup_bdev+0xc5/0x290 block/bdev.c:1136
resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
call_write_iter include/linux/fs.h:2110 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0xa84/0xcb0 fs/read_write.c:590
ksys_write+0x1a0/0x2c0 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 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+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154
traverse+0x14f/0x550 fs/seq_file.c:106
seq_read_iter+0xc5e/0xd60 fs/seq_file.c:195
call_read_iter include/linux/fs.h:2104 [inline]
copy_splice_read+0x662/0xb60 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
do_sendfile+0x515/0xdc0 fs/read_write.c:1301
__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+0xf5/0x240 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 --> &pipe->mutex --> &p->lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&p->lock);
lock(&pipe->mutex);
lock(&p->lock);
lock(&of->mutex);
*** DEADLOCK ***
2 locks held by syz-executor149/5078:
#0: ffff88807de89868 (&pipe->mutex){+.+.}-{3:3}, at: splice_file_to_pipe+0x2e/0x500 fs/splice.c:1292
#1: ffff88802d80b540 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
stack backtrace:
CPU: 0 PID: 5078 Comm: syz-executor149 Not tainted 6.9.0-rc7-syzkaller-00012-gdccb07f2914c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154
traverse+0x14f/0x550 fs/seq_file.c:106
seq_read_iter+0xc5e/0xd60 fs/seq_file.c:195
call_read_iter include/linux/fs.h:2104 [inline]
copy_splice_read+0x662/0xb60 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
do_sendfile+0x515/0xdc0 fs/read_write.c:1301
__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+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7d8d33f8e9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7d8d2b8218 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f7d8d3c9428 RCX: 00007f7d8d33f8e9
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000006
RBP: 00007f7d8d3c9420 R08: 00007ffdc82d7c57 R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000246 R12: 00007f7d8d39606c
R13: 0030656c69662f2e R14: 0079616c7265766f R15: 00007f7d8d39603b
</TASK>
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
next prev parent reply other threads:[~2024-05-08 5:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-27 11:09 [syzbot] [kernfs?] possible deadlock in kernfs_seq_start syzbot
2024-05-08 5:36 ` syzbot [this message]
2024-05-08 23:19 ` Hillf Danton
2024-05-09 6:37 ` Amir Goldstein
2024-05-09 10:48 ` Hillf Danton
2024-05-09 14:52 ` Amir Goldstein
2024-05-09 23:26 ` Hillf Danton
2024-05-10 11:33 ` Hillf Danton
2024-05-10 10:26 ` Hillf Danton
2024-05-10 10:47 ` syzbot
2024-05-08 15:13 ` syzbot
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