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: 95d, last: 5d03h

Sample crash report:

======================================================
WARNING: possible circular locking dependency detected
5.7.0-rc7-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.1/26920 is trying to acquire lock:
ffff888086ecc6b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:807 [inline]
ffff888086ecc6b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_slow fs/namei.c:1546 [inline]
ffff888086ecc6b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: walk_component+0x409/0x6a0 fs/namei.c:1846

but task is already holding lock:
ffff8880a0f0af88 (&sig->exec_update_mutex){+.+.}-{3:3}, at: __do_sys_perf_event_open+0xd89/0x2930 kernel/events/core.c:11582

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+0x156/0x13c0 kernel/locking/mutex.c:1103
       lock_trace+0x45/0xe0 fs/proc/base.c:408
       proc_pid_stack+0xbd/0x1f0 fs/proc/base.c:452
       proc_single_show+0xf7/0x1c0 fs/proc/base.c:758
       seq_read+0x432/0xfd0 fs/seq_file.c:206
       do_loop_readv_writev fs/read_write.c:715 [inline]
       do_loop_readv_writev fs/read_write.c:702 [inline]
       do_iter_read+0x483/0x650 fs/read_write.c:936
       vfs_readv+0xf0/0x160 fs/read_write.c:1054
       do_preadv+0x1bc/0x270 fs/read_write.c:1146
       do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
       entry_SYSCALL_64_after_hwframe+0x49/0xb3

-> #2 (&p->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:956 [inline]
       __mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1103
       seq_read+0x61/0xfd0 fs/seq_file.c:153
       do_loop_readv_writev fs/read_write.c:715 [inline]
       do_loop_readv_writev fs/read_write.c:702 [inline]
       do_iter_read+0x483/0x650 fs/read_write.c:936
       vfs_readv+0xf0/0x160 fs/read_write.c:1054
       kernel_readv fs/splice.c:365 [inline]
       default_file_splice_read+0x4fb/0xa20 fs/splice.c:422
       do_splice_to+0x114/0x160 fs/splice.c:892
       splice_direct_to_actor+0x307/0x980 fs/splice.c:971
       do_splice_direct+0x1b4/0x280 fs/splice.c:1080
       do_sendfile+0x555/0xc50 fs/read_write.c:1521
       __do_sys_sendfile64 fs/read_write.c:1582 [inline]
       __se_sys_sendfile64 fs/read_write.c:1568 [inline]
       __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1568
       do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
       entry_SYSCALL_64_after_hwframe+0x49/0xb3

-> #1 (sb_writers#3){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write+0x230/0x470 fs/super.c:1674
       sb_start_write include/linux/fs.h:1655 [inline]
       mnt_want_write+0x3a/0xb0 fs/namespace.c:354
       ovl_do_remove+0xe9/0xd70 fs/overlayfs/dir.c:862
       vfs_rmdir fs/namei.c:3688 [inline]
       vfs_rmdir+0x195/0x500 fs/namei.c:3667
       do_rmdir+0x371/0x3e0 fs/namei.c:3750
       do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
       entry_SYSCALL_64_after_hwframe+0x49/0xb3

-> #0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:2515 [inline]
       check_prevs_add kernel/locking/lockdep.c:2620 [inline]
       validate_chain kernel/locking/lockdep.c:3237 [inline]
       __lock_acquire+0x2ab1/0x4c50 kernel/locking/lockdep.c:4355
       lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4934
       down_read+0x96/0x420 kernel/locking/rwsem.c:1492
       inode_lock_shared include/linux/fs.h:807 [inline]
       lookup_slow fs/namei.c:1546 [inline]
       walk_component+0x409/0x6a0 fs/namei.c:1846
       lookup_last fs/namei.c:2295 [inline]
       path_lookupat.isra.0+0x180/0x530 fs/namei.c:2319
       filename_lookup+0x1a3/0x3e0 fs/namei.c:2352
       create_local_trace_uprobe+0x87/0x480 kernel/trace/trace_uprobe.c:1575
       perf_uprobe_init+0x132/0x210 kernel/trace/trace_event_perf.c:323
       perf_uprobe_event_init+0xff/0x190 kernel/events/core.c:9478
       perf_try_init_event+0x12a/0x560 kernel/events/core.c:10779
       perf_init_event kernel/events/core.c:10831 [inline]
       perf_event_alloc.part.0+0xe26/0x38c0 kernel/events/core.c:11107
       perf_event_alloc kernel/events/core.c:11486 [inline]
       __do_sys_perf_event_open+0x695/0x2930 kernel/events/core.c:11602
       do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
       entry_SYSCALL_64_after_hwframe+0x49/0xb3

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.1/26920:
 #0: ffff8880a0f0af88 (&sig->exec_update_mutex){+.+.}-{3:3}, at: __do_sys_perf_event_open+0xd89/0x2930 kernel/events/core.c:11582
 #1: ffffffff8c67a5c0 (&pmus_srcu){....}-{0:0}, at: perf_event_alloc.part.0+0xc72/0x38c0 kernel/events/core.c:11105

stack backtrace:
CPU: 0 PID: 26920 Comm: syz-executor.1 Not tainted 5.7.0-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+0x188/0x20d lib/dump_stack.c:118
 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1846
 check_prev_add kernel/locking/lockdep.c:2515 [inline]
 check_prevs_add kernel/locking/lockdep.c:2620 [inline]
 validate_chain kernel/locking/lockdep.c:3237 [inline]
 __lock_acquire+0x2ab1/0x4c50 kernel/locking/lockdep.c:4355
 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4934
 down_read+0x96/0x420 kernel/locking/rwsem.c:1492
 inode_lock_shared include/linux/fs.h:807 [inline]
 lookup_slow fs/namei.c:1546 [inline]
 walk_component+0x409/0x6a0 fs/namei.c:1846
 lookup_last fs/namei.c:2295 [inline]
 path_lookupat.isra.0+0x180/0x530 fs/namei.c:2319
 filename_lookup+0x1a3/0x3e0 fs/namei.c:2352
 create_local_trace_uprobe+0x87/0x480 kernel/trace/trace_uprobe.c:1575
 perf_uprobe_init+0x132/0x210 kernel/trace/trace_event_perf.c:323
 perf_uprobe_event_init+0xff/0x190 kernel/events/core.c:9478
 perf_try_init_event+0x12a/0x560 kernel/events/core.c:10779
 perf_init_event kernel/events/core.c:10831 [inline]
 perf_event_alloc.part.0+0xe26/0x38c0 kernel/events/core.c:11107
 perf_event_alloc kernel/events/core.c:11486 [inline]
 __do_sys_perf_event_open+0x695/0x2930 kernel/events/core.c:11602
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca29
Code: 0d b7 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 b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fed6c154c78 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00000000004f95c0 RCX: 000000000045ca29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000140
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000081e R14: 00000000004caf71 R15: 00007fed6c1556d4

Crashes (5):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Maintainers
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