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Message-ID: <00000000000052a12105c82facde@google.com>
Date: Wed, 28 Jul 2021 07:19:23 -0700
From: syzbot <syzbot+4bdbcaa79e8ee36fe6af@...kaller.appspotmail.com>
To: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-unionfs@...r.kernel.org, miklos@...redi.hu,
mszeredi@...hat.com, syzkaller-bugs@...glegroups.com,
viro@...iv.linux.org.uk
Subject: [syzbot] possible deadlock in iter_file_splice_write (2)
Hello,
syzbot found the following issue on:
HEAD commit: f0fddcec6b62 Merge tag 'for-5.14-rc2-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15a13312300000
kernel config: https://syzkaller.appspot.com/x/.config?x=5dc0e3202ae2f574
dashboard link: https://syzkaller.appspot.com/bug?extid=4bdbcaa79e8ee36fe6af
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10a68b12300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1226e6ca300000
The issue was bisected to:
commit 82a763e61e2b601309d696d4fa514c77d64ee1be
Author: Miklos Szeredi <mszeredi@...hat.com>
Date: Mon Dec 14 14:26:14 2020 +0000
ovl: simplify file splice
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1324e8fc300000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10a4e8fc300000
console output: https://syzkaller.appspot.com/x/log.txt?x=1724e8fc300000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4bdbcaa79e8ee36fe6af@...kaller.appspotmail.com
Fixes: 82a763e61e2b ("ovl: simplify file splice")
======================================================
WARNING: possible circular locking dependency detected
5.14.0-rc2-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor919/8626 is trying to acquire lock:
ffff8880141ed068 (&pipe->mutex/1){+.+.}-{3:3}, at: iter_file_splice_write+0x257/0xf30 fs/splice.c:635
but task is already holding lock:
ffff888029aac460 (sb_writers#5){.+.+}-{0:0}, at: __do_splice fs/splice.c:1144 [inline]
ffff888029aac460 (sb_writers#5){.+.+}-{0:0}, at: __do_sys_splice fs/splice.c:1350 [inline]
ffff888029aac460 (sb_writers#5){.+.+}-{0:0}, at: __se_sys_splice+0x32c/0x430 fs/splice.c:1332
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (sb_writers#5){.+.+}-{0:0}:
lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1763 [inline]
sb_start_write include/linux/fs.h:1833 [inline]
file_start_write+0xc7/0x230 include/linux/fs.h:3040
ovl_write_iter+0x81d/0xdb0 fs/overlayfs/file.c:357
do_iter_readv_writev+0x566/0x770 include/linux/fs.h:2108
do_iter_write+0x16c/0x5f0 fs/read_write.c:866
iter_file_splice_write+0x7c1/0xf30 fs/splice.c:689
do_splice_from fs/splice.c:767 [inline]
do_splice+0xe8e/0x17e0 fs/splice.c:1079
__do_splice fs/splice.c:1144 [inline]
__do_sys_splice fs/splice.c:1350 [inline]
__se_sys_splice+0x32c/0x430 fs/splice.c:1332
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
-> #1 (&ovl_i_mutex_key[depth]){+.+.}-{3:3}:
lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625
down_write+0x97/0x170 kernel/locking/rwsem.c:1406
inode_lock include/linux/fs.h:774 [inline]
ovl_write_iter+0x132/0xdb0 fs/overlayfs/file.c:341
do_iter_readv_writev+0x566/0x770 include/linux/fs.h:2108
do_iter_write+0x16c/0x5f0 fs/read_write.c:866
iter_file_splice_write+0x7c1/0xf30 fs/splice.c:689
do_splice_from fs/splice.c:767 [inline]
do_splice+0xe8e/0x17e0 fs/splice.c:1079
__do_splice fs/splice.c:1144 [inline]
__do_sys_splice fs/splice.c:1350 [inline]
__se_sys_splice+0x32c/0x430 fs/splice.c:1332
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
-> #0 (&pipe->mutex/1){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3051 [inline]
check_prevs_add+0x4f9/0x5b30 kernel/locking/lockdep.c:3174
validate_chain kernel/locking/lockdep.c:3789 [inline]
__lock_acquire+0x4476/0x6100 kernel/locking/lockdep.c:5015
lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625
__mutex_lock_common+0x1ad/0x3770 kernel/locking/mutex.c:959
__mutex_lock kernel/locking/mutex.c:1104 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119
iter_file_splice_write+0x257/0xf30 fs/splice.c:635
do_splice_from fs/splice.c:767 [inline]
do_splice+0xe8e/0x17e0 fs/splice.c:1079
__do_splice fs/splice.c:1144 [inline]
__do_sys_splice fs/splice.c:1350 [inline]
__se_sys_splice+0x32c/0x430 fs/splice.c:1332
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
other info that might help us debug this:
Chain exists of:
&pipe->mutex/1 --> &ovl_i_mutex_key[depth] --> sb_writers#5
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(sb_writers#5);
lock(&ovl_i_mutex_key[depth]);
lock(sb_writers#5);
lock(&pipe->mutex/1);
*** DEADLOCK ***
1 lock held by syz-executor919/8626:
#0: ffff888029aac460 (sb_writers#5){.+.+}-{0:0}, at: __do_splice fs/splice.c:1144 [inline]
#0: ffff888029aac460 (sb_writers#5){.+.+}-{0:0}, at: __do_sys_splice fs/splice.c:1350 [inline]
#0: ffff888029aac460 (sb_writers#5){.+.+}-{0:0}, at: __se_sys_splice+0x32c/0x430 fs/splice.c:1332
stack backtrace:
CPU: 0 PID: 8626 Comm: syz-executor919 Not tainted 5.14.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1ae/0x29f lib/dump_stack.c:105
print_circular_bug+0xb17/0xdc0 kernel/locking/lockdep.c:2009
check_noncircular+0x2cc/0x390 kernel/locking/lockdep.c:2131
check_prev_add kernel/locking/lockdep.c:3051 [inline]
check_prevs_add+0x4f9/0x5b30 kernel/locking/lockdep.c:3174
validate_chain kernel/locking/lockdep.c:3789 [inline]
__lock_acquire+0x4476/0x6100 kernel/locking/lockdep.c:5015
lock_acquire+0x182/0x4a0 kernel/locking/lockdep.c:5625
__mutex_lock_common+0x1ad/0x3770 kernel/locking/mutex.c:959
__mutex_lock kernel/locking/mutex.c:1104 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119
iter_file_splice_write+0x257/0xf30 fs/splice.c:635
do_splice_from fs/splice.c:767 [inline]
do_splice+0xe8e/0x17e0 fs/splice.c:1079
__do_splice fs/splice.c:1144 [inline]
__do_sys_splice fs/splice.c:1350 [inline]
__se_sys_splice+0x32c/0x430 fs/splice.c:1332
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4461b9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7b06be32e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00000000004cb4f0 RCX: 00000000004461b9
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000049b06c R08: 000000000004ffdc R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 3d72696472657070
R13: 0079616c7265766f R14: 69662f7375622f2e R15: 00000000004cb4f8
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches
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