possible deadlock in lookup_slow (2)

From: syzbot
Date: Thu Nov 28 2019 - 19:05:12 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 89d57ddd Merge tag 'media/v5.5-1' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=172becbce00000
kernel config: https://syzkaller.appspot.com/x/.config?x=595c15c951695d1b
dashboard link: https://syzkaller.appspot.com/bug?extid=4821b50cc2e4bd1d0d10
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4821b50cc2e4bd1d0d10@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
5.4.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/23269 is trying to acquire lock:
ffff888092b3e6d0 (&ovl_i_mutex_dir_key[depth]#2){++++}, at: inode_lock_shared include/linux/fs.h:801 [inline]
ffff888092b3e6d0 (&ovl_i_mutex_dir_key[depth]#2){++++}, at: lookup_slow+0x4a/0x80 fs/namei.c:1679

but task is already holding lock:
ffff88805aa057d0 (&sig->cred_guard_mutex){+.+.}, at: __do_sys_perf_event_open+0xeaa/0x2c70 kernel/events/core.c:11257

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #4 (&sig->cred_guard_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:959 [inline]
__mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1136
do_io_accounting+0x1f4/0x820 fs/proc/base.c:2773
proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2822
proc_single_show+0xfd/0x1c0 fs/proc/base.c:756
seq_read+0x4ca/0x1110 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:714 [inline]
do_loop_readv_writev fs/read_write.c:701 [inline]
do_iter_read+0x4a4/0x660 fs/read_write.c:935
vfs_readv+0xf0/0x160 fs/read_write.c:997
kernel_readv fs/splice.c:359 [inline]
default_file_splice_read+0x482/0x8a0 fs/splice.c:414
do_splice_to+0x127/0x180 fs/splice.c:877
splice_direct_to_actor+0x2d2/0x970 fs/splice.c:954
do_splice_direct+0x1da/0x2a0 fs/splice.c:1063
do_sendfile+0x597/0xd00 fs/read_write.c:1464
__do_sys_sendfile64 fs/read_write.c:1525 [inline]
__se_sys_sendfile64 fs/read_write.c:1511 [inline]
__x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #3 (&p->lock){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:959 [inline]
__mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121
seq_read+0x71/0x1110 fs/seq_file.c:161
proc_reg_read+0x1fc/0x2c0 fs/proc/inode.c:223
do_loop_readv_writev fs/read_write.c:714 [inline]
do_loop_readv_writev fs/read_write.c:701 [inline]
do_iter_read+0x4a4/0x660 fs/read_write.c:935
vfs_readv+0xf0/0x160 fs/read_write.c:997
kernel_readv fs/splice.c:359 [inline]
default_file_splice_read+0x482/0x8a0 fs/splice.c:414
do_splice_to+0x127/0x180 fs/splice.c:877
splice_direct_to_actor+0x2d2/0x970 fs/splice.c:954
do_splice_direct+0x1da/0x2a0 fs/splice.c:1063
do_sendfile+0x597/0xd00 fs/read_write.c:1464
__do_sys_sendfile64 fs/read_write.c:1525 [inline]
__se_sys_sendfile64 fs/read_write.c:1511 [inline]
__x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (sb_writers#4){.+.+}:
percpu_down_read include/linux/percpu-rwsem.h:40 [inline]
__sb_start_write+0x241/0x460 fs/super.c:1672
sb_start_write include/linux/fs.h:1650 [inline]
mnt_want_write+0x3f/0xc0 fs/namespace.c:354
ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:21
ovl_create_object+0xb3/0x2c0 fs/overlayfs/dir.c:596
ovl_create+0x28/0x30 fs/overlayfs/dir.c:627
lookup_open+0x12d5/0x1a90 fs/namei.c:3224
do_last fs/namei.c:3314 [inline]
path_openat+0x14a7/0x46d0 fs/namei.c:3525
do_filp_open+0x1a1/0x280 fs/namei.c:3555
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
ksys_open include/linux/syscalls.h:1385 [inline]
__do_sys_creat fs/open.c:1155 [inline]
__se_sys_creat fs/open.c:1153 [inline]
__x64_sys_creat+0x61/0x80 fs/open.c:1153
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&ovl_i_mutex_dir_key[depth]){++++}:
down_write_killable+0x96/0x170 kernel/locking/rwsem.c:1545
iterate_dir+0x414/0x5e0 fs/readdir.c:57
ovl_dir_read fs/overlayfs/readdir.c:309 [inline]
ovl_dir_read_merged+0x199/0x500 fs/overlayfs/readdir.c:374
ovl_cache_get fs/overlayfs/readdir.c:426 [inline]
ovl_iterate+0x750/0xc50 fs/overlayfs/readdir.c:752
iterate_dir+0x208/0x5e0 fs/readdir.c:67
ksys_getdents64+0x1ce/0x320 fs/readdir.c:372
__do_sys_getdents64 fs/readdir.c:391 [inline]
__se_sys_getdents64 fs/readdir.c:388 [inline]
__x64_sys_getdents64+0x73/0xb0 fs/readdir.c:388
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&ovl_i_mutex_dir_key[depth]#2){++++}:
check_prev_add kernel/locking/lockdep.c:2476 [inline]
check_prevs_add kernel/locking/lockdep.c:2581 [inline]
validate_chain kernel/locking/lockdep.c:2971 [inline]
__lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485
down_read+0x95/0x430 kernel/locking/rwsem.c:1495
inode_lock_shared include/linux/fs.h:801 [inline]
lookup_slow+0x4a/0x80 fs/namei.c:1679
walk_component+0x747/0x1ff0 fs/namei.c:1800
lookup_last fs/namei.c:2263 [inline]
path_lookupat.isra.0+0x1f5/0x8d0 fs/namei.c:2308
filename_lookup+0x1b0/0x3f0 fs/namei.c:2338
kern_path+0x36/0x40 fs/namei.c:2424
create_local_trace_uprobe+0x87/0x4a0 kernel/trace/trace_uprobe.c:1542
perf_uprobe_init+0x131/0x210 kernel/trace/trace_event_perf.c:323
perf_uprobe_event_init+0x106/0x1a0 kernel/events/core.c:9162
perf_try_init_event+0x135/0x590 kernel/events/core.c:10462
perf_init_event kernel/events/core.c:10514 [inline]
perf_event_alloc.part.0+0x1571/0x3720 kernel/events/core.c:10794
perf_event_alloc kernel/events/core.c:10676 [inline]
__do_sys_perf_event_open+0x6f8/0x2c70 kernel/events/core.c:11277
__se_sys_perf_event_open kernel/events/core.c:11151 [inline]
__x64_sys_perf_event_open+0xbe/0x150 kernel/events/core.c:11151
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
&ovl_i_mutex_dir_key[depth]#2 --> &p->lock --> &sig->cred_guard_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sig->cred_guard_mutex);
lock(&p->lock);
lock(&sig->cred_guard_mutex);
lock(&ovl_i_mutex_dir_key[depth]#2);

*** DEADLOCK ***

2 locks held by syz-executor.3/23269:
#0: ffff88805aa057d0 (&sig->cred_guard_mutex){+.+.}, at: __do_sys_perf_event_open+0xeaa/0x2c70 kernel/events/core.c:11257
#1: ffffffff8ad0e3e8 (&pmus_srcu){....}, at: perf_event_alloc.part.0+0xede/0x3720 kernel/events/core.c:10790

stack backtrace:
CPU: 0 PID: 23269 Comm: syz-executor.3 Not tainted 5.4.0-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+0x197/0x210 lib/dump_stack.c:118
print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1685
check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1809
check_prev_add kernel/locking/lockdep.c:2476 [inline]
check_prevs_add kernel/locking/lockdep.c:2581 [inline]
validate_chain kernel/locking/lockdep.c:2971 [inline]
__lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485
down_read+0x95/0x430 kernel/locking/rwsem.c:1495
inode_lock_shared include/linux/fs.h:801 [inline]
lookup_slow+0x4a/0x80 fs/namei.c:1679
walk_component+0x747/0x1ff0 fs/namei.c:1800
lookup_last fs/namei.c:2263 [inline]
path_lookupat.isra.0+0x1f5/0x8d0 fs/namei.c:2308
filename_lookup+0x1b0/0x3f0 fs/namei.c:2338
kern_path+0x36/0x40 fs/namei.c:2424
create_local_trace_uprobe+0x87/0x4a0 kernel/trace/trace_uprobe.c:1542
perf_uprobe_init+0x131/0x210 kernel/trace/trace_event_perf.c:323
perf_uprobe_event_init+0x106/0x1a0 kernel/events/core.c:9162
perf_try_init_event+0x135/0x590 kernel/events/core.c:10462
perf_init_event kernel/events/core.c:10514 [inline]
perf_event_alloc.part.0+0x1571/0x3720 kernel/events/core.c:10794
perf_event_alloc kernel/events/core.c:10676 [inline]
__do_sys_perf_event_open+0x6f8/0x2c70 kernel/events/core.c:11277
__se_sys_perf_event_open kernel/events/core.c:11151 [inline]
__x64_sys_perf_event_open+0xbe/0x150 kernel/events/core.c:11151
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a649
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff838acbc78 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 000000000045a649
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000180
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 00007ff838acc6d4
R13: 00000000004c7bb1 R14: 00000000004ddb90 R15: 00000000ffffffff

---
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