possible deadlock in lock

possible deadlock in lock_trace
Status: upstream: reported C repro on 2019/04/19 09:51
Reported-by: syzbot+15de275074ca85b268c7@syzkaller.appspotmail.com
First crash: 1126d, last: 669d

Fix bisection: failed (bisect log)

similar bugs (7):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.19	possible deadlock in lock_trace	syz		error	42	611d	1117d	0/1	upstream: reported syz repro on 2019/04/28 18:16
android-49	possible deadlock in lock_trace	C			7424	897d	1134d	0/3	public: reported C repro on 2019/04/12 00:00
upstream	possible deadlock in lock_trace (2)				3	1098d	1128d	0/22	auto-closed as invalid on 2019/10/25 08:41
upstream	possible deadlock in lock_trace	C			1847	1150d	1631d	0/22	closed as dup on 2017/12/12 21:59
upstream	possible deadlock in lock_trace (3)	syz	inconclusive	done	69	777d	912d	17/22	fixed on 2020/08/18 22:40
android-414	possible deadlock in lock_trace	syz			203	1142d	1134d	0/1	public: reported syz repro on 2019/04/12 00:01
android-44	possible deadlock in lock_trace	C			41	904d	1134d	0/2	public: reported C repro on 2019/04/11 08:44

Sample crash report:

======================================================
WARNING: possible circular locking dependency detected
4.14.175-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor993/6341 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.}, at: [<ffffffff81a45d4f>] lock_trace+0x3f/0xc0 fs/proc/base.c:407

but task is already holding lock:
 (&p->lock){+.+.}, at: [<ffffffff8192f06a>] seq_read+0xba/0x1160 fs/seq_file.c:165

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->lock){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
       seq_read+0xba/0x1160 fs/seq_file.c:165
       do_loop_readv_writev fs/read_write.c:695 [inline]
       do_loop_readv_writev fs/read_write.c:682 [inline]
       do_iter_read+0x3e3/0x5a0 fs/read_write.c:919
       vfs_readv+0xd3/0x130 fs/read_write.c:981
       kernel_readv fs/splice.c:361 [inline]
       default_file_splice_read+0x41d/0x870 fs/splice.c:416
       do_splice_to+0xfb/0x150 fs/splice.c:880
       splice_direct_to_actor+0x20a/0x730 fs/splice.c:952
       do_splice_direct+0x164/0x210 fs/splice.c:1061
       do_sendfile+0x469/0xaf0 fs/read_write.c:1441
       SYSC_sendfile64 fs/read_write.c:1502 [inline]
       SyS_sendfile64+0xff/0x110 fs/read_write.c:1488
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #2 (sb_writers#3){.+.+}:
       percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
       __sb_start_write+0x1a1/0x2e0 fs/super.c:1363
       sb_start_write include/linux/fs.h:1549 [inline]
       mnt_want_write+0x3a/0xb0 fs/namespace.c:386
       ovl_create_object+0x75/0x1d0 fs/overlayfs/dir.c:538
       lookup_open+0x10e8/0x1750 fs/namei.c:3241
       do_last fs/namei.c:3334 [inline]
       path_openat+0xfc1/0x3c50 fs/namei.c:3569
       do_filp_open+0x18e/0x250 fs/namei.c:3603
       do_sys_open+0x29d/0x3f0 fs/open.c:1081
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #1 (&ovl_i_mutex_dir_key[depth]){++++}:
       down_read+0x37/0xa0 kernel/locking/rwsem.c:24
       inode_lock_shared include/linux/fs.h:729 [inline]
       do_last fs/namei.c:3333 [inline]
       path_openat+0x185a/0x3c50 fs/namei.c:3569
       do_filp_open+0x18e/0x250 fs/namei.c:3603
       do_open_execat+0xda/0x430 fs/exec.c:849
       do_execveat_common.isra.0+0x694/0x1c70 fs/exec.c:1740
       do_execve fs/exec.c:1847 [inline]
       SYSC_execve fs/exec.c:1928 [inline]
       SyS_execve+0x34/0x40 fs/exec.c:1923
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 (&sig->cred_guard_mutex){+.+.}:
       lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3994
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
       lock_trace+0x3f/0xc0 fs/proc/base.c:407
       proc_pid_syscall+0x81/0x1f0 fs/proc/base.c:639
       proc_single_show+0xe7/0x150 fs/proc/base.c:761
       seq_read+0x4d2/0x1160 fs/seq_file.c:237
       do_loop_readv_writev fs/read_write.c:695 [inline]
       do_loop_readv_writev fs/read_write.c:682 [inline]
       do_iter_read+0x3e3/0x5a0 fs/read_write.c:919
       vfs_readv+0xd3/0x130 fs/read_write.c:981
       kernel_readv fs/splice.c:361 [inline]
       default_file_splice_read+0x41d/0x870 fs/splice.c:416
       do_splice_to+0xfb/0x150 fs/splice.c:880
       splice_direct_to_actor+0x20a/0x730 fs/splice.c:952
       do_splice_direct+0x164/0x210 fs/splice.c:1061
       do_sendfile+0x469/0xaf0 fs/read_write.c:1441
       SYSC_sendfile64 fs/read_write.c:1502 [inline]
       SyS_sendfile64+0xff/0x110 fs/read_write.c:1488
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

other info that might help us debug this:

Chain exists of:
  &sig->cred_guard_mutex --> sb_writers#3 --> &p->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&p->lock);
                               lock(sb_writers#3);
                               lock(&p->lock);
  lock(&sig->cred_guard_mutex);

 *** DEADLOCK ***

2 locks held by syz-executor993/6341:
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff818b2945>] file_start_write include/linux/fs.h:2708 [inline]
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff818b2945>] do_sendfile+0x865/0xaf0 fs/read_write.c:1440
 #1:  (&p->lock){+.+.}, at: [<ffffffff8192f06a>] seq_read+0xba/0x1160 fs/seq_file.c:165

stack backtrace:
CPU: 0 PID: 6341 Comm: syz-executor993 Not tainted 4.14.175-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x13e/0x194 lib/dump_stack.c:58
 print_circular_bug.isra.0.cold+0x1c4/0x282 kernel/locking/lockdep.c:1258
 check_prev_add kernel/locking/lockdep.c:1901 [inline]
 check_prevs_add kernel/locking/lockdep.c:2018 [inline]
 validate_chain kernel/locking/lockdep.c:2460 [inline]
 __lock_acquire+0x2cb3/0x4620 kernel/locking/lockdep.c:3487
 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3994
 __mutex_lock_common kernel/locking/mutex.c:756 [inline]
 __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
 lock_trace+0x3f/0xc0 fs/proc/base.c:407
 proc_pid_syscall+0x81/0x1f0 fs/proc/base.c:639
 proc_single_show+0xe7/0x150 fs/proc/base.c:761
 seq_read+0x4d2/0x1160 fs/seq_file.c:237
 do_loop_readv_writev fs/read_write.c:695 [inline]
 do_loop_readv_writev fs/read_write.c:682 [inline]
 do_iter_read+0x3e3/0x5a0 fs/read_write.c:919
 vfs_readv+0xd3/0x130 fs/read_write.c:981
 kernel_readv fs/splice.c:361 [inline]
 default_file_splice_read+0x41d/0x870 fs/splice.c:416
 do_splice_to+0xfb/0x150 fs/splice.c:880
 splice_direct_to_actor+0x20a/0x730 fs/splice.c:952
 do_splice_direct+0x164/0x210 fs/splice.c:1061
 do_sendfile+0x469/0xaf0 fs/read_write.c:1441
 SYSC_sendfile64 fs/read_write.c:1502 [inline]
 SyS_sendfile64+0xff/0x110 fs/read_write.c:1488
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x440389
RSP: 002b:00007fffe

Crashes (146):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci2-linux-4-14	2020/04/04 09:35	linux-4.14.y	4520f06b03ae	ef26b610	.config	log	report	syz	C
ci2-linux-4-14	2020/01/22 13:25	linux-4.14.y	c1141b3aab36	8eda0b95	.config	log	report	syz	C
ci2-linux-4-14	2020/07/19 21:29	linux-4.14.y	b850307b279c	9c812472	.config	log	report
ci2-linux-4-14	2020/07/14 09:14	linux-4.14.y	b850307b279c	ce4c95b3	.config	log	report
ci2-linux-4-14	2020/06/25 01:57	linux-4.14.y	b850307b279c	9d60b18e	.config	log	report
ci2-linux-4-14	2020/06/14 09:07	linux-4.14.y	b850307b279c	a61674a5	.config	log	report
ci2-linux-4-14	2020/06/09 11:51	linux-4.14.y	c6db52a88798	0d60b78a	.config	log	report
ci2-linux-4-14	2020/06/07 05:31	linux-4.14.y	c6db52a88798	e6b89e4e	.config	log	report
ci2-linux-4-14	2020/06/01 21:10	linux-4.14.y	4f68020fef1c	a0331e89	.config	log	report
ci2-linux-4-14	2020/05/26 10:04	linux-4.14.y	a41ba30d9df2	8ca3b7d2	.config	log	report
ci2-linux-4-14	2020/05/22 16:44	linux-4.14.y	a41ba30d9df2	4afdfa20	.config	log	report
ci2-linux-4-14	2020/05/21 01:00	linux-4.14.y	a41ba30d9df2	4afdfa20	.config	log	report
ci2-linux-4-14	2020/05/07 05:06	linux-4.14.y	d71f695ce745	4618eb2d	.config	log	report
ci2-linux-4-14	2020/05/02 09:50	linux-4.14.y	050272a0423e	bc734e7a	.config	log	report
ci2-linux-4-14	2020/04/25 06:04	linux-4.14.y	050272a0423e	03d97a1b	.config	log	report
ci2-linux-4-14	2020/04/24 18:37	linux-4.14.y	050272a0423e	03d97a1b	.config	log	report
ci2-linux-4-14	2020/04/18 13:11	linux-4.14.y	c10b57a567e4	435c6d53	.config	log	report
ci2-linux-4-14	2020/04/17 07:39	linux-4.14.y	c10b57a567e4	18397578	.config	log	report
ci2-linux-4-14	2020/04/16 22:21	linux-4.14.y	c10b57a567e4	c743fcb3	.config	log	report
ci2-linux-4-14	2020/04/16 07:27	linux-4.14.y	c10b57a567e4	c743fcb3	.config	log	report
ci2-linux-4-14	2020/04/15 17:57	linux-4.14.y	c10b57a567e4	3f3c5574	.config	log	report
ci2-linux-4-14	2020/04/13 12:28	linux-4.14.y	c10b57a567e4	17a986e5	.config	log	report
ci2-linux-4-14	2020/04/12 07:51	linux-4.14.y	4520f06b03ae	a8c6a3f8	.config	log	report
ci2-linux-4-14	2020/04/12 03:38	linux-4.14.y	4520f06b03ae	a8c6a3f8	.config	log	report
ci2-linux-4-14	2020/04/10 18:10	linux-4.14.y	4520f06b03ae	a8c6a3f8	.config	log	report
ci2-linux-4-14	2020/04/08 22:52	linux-4.14.y	4520f06b03ae	db9bcd4b	.config	log	report
ci2-linux-4-14	2020/04/03 04:04	linux-4.14.y	4520f06b03ae	a34e2c33	.config	log	report
ci2-linux-4-14	2020/04/02 12:54	linux-4.14.y	01364dad1d45	a34e2c33	.config	log	report
ci2-linux-4-14	2020/04/01 23:43	linux-4.14.y	01364dad1d45	a34e2c33	.config	log	report
ci2-linux-4-14	2020/04/01 22:23	linux-4.14.y	01364dad1d45	a34e2c33	.config	log	report
ci2-linux-4-14	2020/04/01 18:10	linux-4.14.y	01364dad1d45	a34e2c33	.config	log	report
ci2-linux-4-14	2020/04/01 00:43	linux-4.14.y	01364dad1d45	a34e2c33	.config	log	report
ci2-linux-4-14	2020/03/30 23:13	linux-4.14.y	01364dad1d45	c8d1cc20	.config	log	report
ci2-linux-4-14	2020/03/30 10:52	linux-4.14.y	01364dad1d45	c8d1cc20	.config	log	report
ci2-linux-4-14	2020/03/30 09:52	linux-4.14.y	01364dad1d45	c8d1cc20	.config	log	report
ci2-linux-4-14	2020/03/30 06:01	linux-4.14.y	01364dad1d45	05736b29	.config	log	report
ci2-linux-4-14	2020/03/30 04:50	linux-4.14.y	01364dad1d45	05736b29	.config	log	report
ci2-linux-4-14	2020/03/30 02:40	linux-4.14.y	01364dad1d45	05736b29	.config	log	report
ci2-linux-4-14	2020/03/28 00:48	linux-4.14.y	01364dad1d45	831e9a81	.config	log	report
ci2-linux-4-14	2020/03/26 00:43	linux-4.14.y	01364dad1d45	e8e6c7d2	.config	log	report
ci2-linux-4-14	2020/03/22 21:10	linux-4.14.y	01364dad1d45	78267cec	.config	log	report
ci2-linux-4-14	2020/03/22 19:48	linux-4.14.y	01364dad1d45	78267cec	.config	log	report
ci2-linux-4-14	2020/03/17 14:45	linux-4.14.y	12cd844a39ed	749688d2	.config	log	report
ci2-linux-4-14	2020/03/16 21:31	linux-4.14.y	12cd844a39ed	749688d2	.config	log	report
ci2-linux-4-14	2020/03/13 08:11	linux-4.14.y	12cd844a39ed	fd69032d	.config	log	report
ci2-linux-4-14	2020/03/13 03:31	linux-4.14.y	12cd844a39ed	d850e9d0	.config	log	report
ci2-linux-4-14	2020/03/11 11:14	linux-4.14.y	78d697fc93f9	e103bc9e	.config	log	report
ci2-linux-4-14	2020/03/11 09:53	linux-4.14.y	78d697fc93f9	35f53e45	.config	log	report
ci2-linux-4-14	2019/04/19 08:50	linux-4.14.y	58b454ebf81e	b0e8efcb	.config	log	report