Hello,
syzbot found the following crash on:
HEAD commit: 5a6fcbea Add linux-next specific files for 20191115
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=127ba426e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=8eac90e6ae4ab399
dashboard link: https://syzkaller.appspot.com/bug?extid=985c8a3c7f3668d31a49
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+985c8a3c7f3668d31a49@xxxxxxxxxxxxxxxxxxxxxxxxx
======================================================
WARNING: possible circular locking dependency detected
5.4.0-rc7-next-20191115 #0 Not tainted
------------------------------------------------------
syz-executor.3/3829 is trying to acquire lock:
ffff888096981810 (&sig->cred_guard_mutex){+.+.}, at: lock_trace+0x4a/0xe0
fs/proc/base.c:406
but task is already holding lock:
ffff88809611df40 (&p->lock){+.+.}, at: seq_read+0x71/0x1170
fs/seq_file.c:161
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #4 (&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+0x71/0x1170 fs/seq_file.c:161
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+0x2d3/0x970 fs/splice.c:955
do_splice_direct+0x1da/0x2a0 fs/splice.c:1064
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 (sb_writers#3){.+.+}:
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_xattr_set+0x53/0x5b0 fs/overlayfs/inode.c:329
ovl_posix_acl_xattr_set+0x33a/0x9a0 fs/overlayfs/super.c:910
__vfs_setxattr+0x11f/0x180 fs/xattr.c:150
__vfs_setxattr_noperm+0x11c/0x410 fs/xattr.c:181
vfs_setxattr+0xda/0x100 fs/xattr.c:224
setxattr+0x26f/0x380 fs/xattr.c:451
path_setxattr+0x197/0x1b0 fs/xattr.c:470
__do_sys_setxattr fs/xattr.c:485 [inline]
__se_sys_setxattr fs/xattr.c:481 [inline]
__x64_sys_setxattr+0xc4/0x150 fs/xattr.c:481
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #2 (&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
-> #1 (&ovl_i_mutex_dir_key[depth]#2){++++}:
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:1683
walk_component+0x747/0x1ff0 fs/namei.c:1804
lookup_last fs/namei.c:2267 [inline]
path_lookupat.isra.0+0x1f5/0x8d0 fs/namei.c:2312
filename_lookup+0x1b0/0x3f0 fs/namei.c:2342
kern_path+0x36/0x40 fs/namei.c:2428
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:9138
perf_try_init_event+0x135/0x590 kernel/events/core.c:10438
perf_init_event kernel/events/core.c:10490 [inline]
perf_event_alloc.part.0+0x14ed/0x3600 kernel/events/core.c:10773
perf_event_alloc kernel/events/core.c:11140 [inline]
__do_sys_perf_event_open+0x6f8/0x2be0 kernel/events/core.c:11256
__se_sys_perf_event_open kernel/events/core.c:11130 [inline]
__x64_sys_perf_event_open+0xbe/0x150 kernel/events/core.c:11130
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (&sig->cred_guard_mutex){+.+.}:
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
__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
lock_trace+0x4a/0xe0 fs/proc/base.c:406
proc_pid_syscall+0x8a/0x220 fs/proc/base.c:635
proc_single_show+0xf0/0x170 fs/proc/base.c:756
seq_read+0x4ca/0x1170 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
do_preadv+0x1c4/0x280 fs/read_write.c:1089
__do_sys_preadv fs/read_write.c:1139 [inline]
__se_sys_preadv fs/read_write.c:1134 [inline]
__x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1134
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:
&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 ***
1 lock held by syz-executor.3/3829:
#0: ffff88809611df40 (&p->lock){+.+.}, at: seq_read+0x71/0x1170
fs/seq_file.c:161
stack backtrace:
CPU: 0 PID: 3829 Comm: syz-executor.3 Not tainted 5.4.0-rc7-next-20191115 #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
__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
lock_trace+0x4a/0xe0 fs/proc/base.c:406
proc_pid_syscall+0x8a/0x220 fs/proc/base.c:635
proc_single_show+0xf0/0x170 fs/proc/base.c:756
seq_read+0x4ca/0x1170 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
do_preadv+0x1c4/0x280 fs/read_write.c:1089
__do_sys_preadv fs/read_write.c:1139 [inline]
__se_sys_preadv fs/read_write.c:1134 [inline]
__x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1134
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a659
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:00007f2247981c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045a659
RDX: 00000000000001e3 RSI: 00000000200013c0 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f22479826d4
R13: 00000000004c7ec1 R14: 00000000004dde10 R15: 00000000ffffffff
---
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