possible deadlock in walk

possible deadlock in walk_component
Status: upstream: reported on 2020/03/02 00:43
Reported-by: syzbot+a84f8e843059b8bb50c3@syzkaller.appspotmail.com
First crash: 235d, last: 19d

similar bugs (1):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
linux-4.19	possible deadlock in walk_component			24	1d02h	107d	0/1	upstream: reported on 2020/07/06 08:23

Sample crash report:

======================================================
WARNING: possible circular locking dependency detected
5.9.0-rc7-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.5/6008 is trying to acquire lock:
ffff88804035bbf0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:789 [inline]
ffff88804035bbf0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_slow fs/namei.c:1560 [inline]
ffff88804035bbf0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: walk_component+0x409/0x6a0 fs/namei.c:1860

but task is already holding lock:
ffff888045e87948 (&sig->exec_update_mutex){+.+.}-{3:3}, at: __do_sys_perf_event_open+0xda1/0x2cb0 kernel/events/core.c:11704

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&sig->exec_update_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:956 [inline]
       __mutex_lock+0x134/0x10e0 kernel/locking/mutex.c:1103
       lock_trace fs/proc/base.c:408 [inline]
       proc_pid_personality+0x4a/0x170 fs/proc/base.c:3116
       proc_single_show+0x116/0x1e0 fs/proc/base.c:775
       seq_read+0x432/0x1070 fs/seq_file.c:208
       do_loop_readv_writev fs/read_write.c:742 [inline]
       do_loop_readv_writev fs/read_write.c:729 [inline]
       do_iter_read+0x48e/0x6e0 fs/read_write.c:963
       vfs_readv+0xe5/0x150 fs/read_write.c:1081
       do_preadv fs/read_write.c:1173 [inline]
       __do_sys_preadv fs/read_write.c:1223 [inline]
       __se_sys_preadv fs/read_write.c:1218 [inline]
       __x64_sys_preadv+0x231/0x310 fs/read_write.c:1218
       do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #2 (&p->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:956 [inline]
       __mutex_lock+0x134/0x10e0 kernel/locking/mutex.c:1103
       seq_read+0x61/0x1070 fs/seq_file.c:155
       do_loop_readv_writev fs/read_write.c:742 [inline]
       do_loop_readv_writev fs/read_write.c:729 [inline]
       do_iter_read+0x48e/0x6e0 fs/read_write.c:963
       vfs_readv+0xe5/0x150 fs/read_write.c:1081
       kernel_readv fs/splice.c:355 [inline]
       default_file_splice_read.constprop.0+0x4e6/0x9e0 fs/splice.c:412
       do_splice_to+0x137/0x170 fs/splice.c:871
       splice_direct_to_actor+0x307/0x980 fs/splice.c:950
       do_splice_direct+0x1b3/0x280 fs/splice.c:1059
       do_sendfile+0x55f/0xd40 fs/read_write.c:1548
       __do_sys_sendfile64 fs/read_write.c:1609 [inline]
       __se_sys_sendfile64 fs/read_write.c:1595 [inline]
       __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1595
       do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #1 (sb_writers#4){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write+0x228/0x450 fs/super.c:1672
       sb_start_write include/linux/fs.h:1643 [inline]
       mnt_want_write+0x3a/0xb0 fs/namespace.c:354
       ovl_create_object+0x96/0x290 fs/overlayfs/dir.c:625
       lookup_open.isra.0+0xf85/0x1350 fs/namei.c:3103
       open_last_lookups fs/namei.c:3177 [inline]
       path_openat+0x96d/0x2730 fs/namei.c:3365
       do_filp_open+0x17e/0x3c0 fs/namei.c:3395
       do_sys_openat2+0x16d/0x420 fs/open.c:1168
       do_sys_open fs/open.c:1184 [inline]
       __do_sys_open fs/open.c:1192 [inline]
       __se_sys_open fs/open.c:1188 [inline]
       __x64_sys_open+0x119/0x1c0 fs/open.c:1188
       do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:2496 [inline]
       check_prevs_add kernel/locking/lockdep.c:2601 [inline]
       validate_chain kernel/locking/lockdep.c:3218 [inline]
       __lock_acquire+0x2a96/0x5780 kernel/locking/lockdep.c:4441
       lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5029
       down_read+0x96/0x420 kernel/locking/rwsem.c:1492
       inode_lock_shared include/linux/fs.h:789 [inline]
       lookup_slow fs/namei.c:1560 [inline]
       walk_component+0x409/0x6a0 fs/namei.c:1860
       lookup_last fs/namei.c:2309 [inline]
       path_lookupat+0x1ba/0x830 fs/namei.c:2333
       filename_lookup+0x19f/0x560 fs/namei.c:2366
       create_local_trace_uprobe+0x87/0x4e0 kernel/trace/trace_uprobe.c:1574
       perf_uprobe_init+0x132/0x210 kernel/trace/trace_event_perf.c:323
       perf_uprobe_event_init+0xff/0x1c0 kernel/events/core.c:9580
       perf_try_init_event+0x12a/0x560 kernel/events/core.c:10899
       perf_init_event kernel/events/core.c:10951 [inline]
       perf_event_alloc.part.0+0xdee/0x37d0 kernel/events/core.c:11229
       perf_event_alloc kernel/events/core.c:11608 [inline]
       __do_sys_perf_event_open+0x72c/0x2cb0 kernel/events/core.c:11724
       do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

other info that might help us debug this:

Chain exists of:
  &ovl_i_mutex_dir_key[depth] --> &p->lock --> &sig->exec_update_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sig->exec_update_mutex);
                               lock(&p->lock);
                               lock(&sig->exec_update_mutex);
  lock(&ovl_i_mutex_dir_key[depth]);

 *** DEADLOCK ***

2 locks held by syz-executor.5/6008:
 #0: ffff888045e87948 (&sig->exec_update_mutex){+.+.}-{3:3}, at: __do_sys_perf_event_open+0xda1/0x2cb0 kernel/events/core.c:11704
 #1: ffffffff8d44d1e0 (&pmus_srcu){....}-{0:0}, at: perf_event_alloc.part.0+0xc41/0x37d0 kernel/events/core.c:11227

stack backtrace:
CPU: 1 PID: 6008 Comm: syz-executor.5 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 check_noncircular+0x324/0x3e0 kernel/locking/lockdep.c:1827
 check_prev_add kernel/locking/lockdep.c:2496 [inline]
 check_prevs_add kernel/locking/lockdep.c:2601 [inline]
 validate_chain kernel/locking/lockdep.c:3218 [inline]
 __lock_acquire+0x2a96/0x5780 kernel/locking/lockdep.c:4441
 lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5029
 down_read+0x96/0x420 kernel/locking/rwsem.c:1492
 inode_lock_shared include/linux/fs.h:789 [inline]
 lookup_slow fs/namei.c:1560 [inline]
 walk_component+0x409/0x6a0 fs/namei.c:1860
 lookup_last fs/namei.c:2309 [inline]
 path_lookupat+0x1ba/0x830 fs/namei.c:2333
 filename_lookup+0x19f/0x560 fs/namei.c:2366
 create_local_trace_uprobe+0x87/0x4e0 kernel/trace/trace_uprobe.c:1574
 perf_uprobe_init+0x132/0x210 kernel/trace/trace_event_perf.c:323
 perf_uprobe_event_init+0xff/0x1c0 kernel/events/core.c:9580
 perf_try_init_event+0x12a/0x560 kernel/events/core.c:10899
 perf_init_event kernel/events/core.c:10951 [inline]
 perf_event_alloc.part.0+0xdee/0x37d0 kernel/events/core.c:11229
 perf_event_alloc kernel/events/core.c:11608 [inline]
 __do_sys_perf_event_open+0x72c/0x2cb0 kernel/events/core.c:11724
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45dd99
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff1fcb19c78 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 0000000000024cc0 RCX: 000000000045dd99
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000180
RBP: 000000000118c168 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 000000000118c124
R13: 00007ffd61a8458f R14: 00007ff1fcb1a9c0 R15: 000000000118c124

Crashes (11):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Maintainers
ci-upstream-kasan-gce-selinux-root	2020/10/01 13:42	upstream	60e72093	a9767fb2	.config	log	report	info	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-selinux-root	2020/09/07 10:01	upstream	f4d51dff	abf9ba4f	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-smack-root	2020/09/06 22:39	upstream	dd9fb9bb	abf9ba4f	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-root	2020/08/07 08:31	upstream	d6efb3ac	cb436c69	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-root	2020/08/06 13:10	upstream	47ec5303	1f122f88	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-selinux-root	2020/05/29 00:16	upstream	75caf310	0d951763	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-smack-root	2020/04/07 17:39	upstream	7e634208	99a96044	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-selinux-root	2020/03/05 10:58	upstream	63623fd4	c88c7b75	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-smack-root	2020/03/01 11:05	upstream	63623fd4	c88c7b75	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-smack-root	2020/02/29 01:45	upstream	f8788d86	59b57593	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-linux-next-kasan-gce-root	2020/08/17 17:08	linux-next	0f1fa584	424dd8e7	.config	log	report		linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk