======================================================
WARNING: possible circular locking dependency detected
5.6.0-rc2-next-20200218-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.1/12868 is trying to acquire lock:
ffff8880a7bf3c90 (&sig->cred_guard_mutex){+.+.}, at: lock_trace+0x4a/0xe0 fs/proc/base.c:408
but task is already holding lock:
ffff8880a96aff40 (&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:
-> #3 (&p->lock){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:956 [inline]
__mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1103
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
seq_read+0x71/0x1170 fs/seq_file.c:161
proc_reg_read+0x1f8/0x2b0 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:1053
kernel_readv fs/splice.c:365 [inline]
default_file_splice_read+0x4fb/0xa20 fs/splice.c:422
do_splice_to+0x127/0x180 fs/splice.c:892
splice_direct_to_actor+0x320/0xa30 fs/splice.c:971
do_splice_direct+0x1da/0x2a0 fs/splice.c:1080
do_sendfile+0x597/0xd00 fs/read_write.c:1520
__do_sys_sendfile64 fs/read_write.c:1581 [inline]
__se_sys_sendfile64 fs/read_write.c:1567 [inline]
__x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1567
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #2 (sb_writers#3){.+.+}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write+0x255/0x4a0 fs/super.c:1674
sb_start_write include/linux/fs.h:1649 [inline]
mnt_want_write+0x3f/0xc0 fs/namespace.c:354
ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:21
ovl_do_remove+0xe9/0xd70 fs/overlayfs/dir.c:837
ovl_unlink+0x18/0x20 fs/overlayfs/dir.c:882
vfs_unlink+0x2d7/0x620 fs/namei.c:4073
do_unlinkat+0x3f7/0x6d0 fs/namei.c:4137
__do_sys_unlink fs/namei.c:4184 [inline]
__se_sys_unlink fs/namei.c:4182 [inline]
__x64_sys_unlink+0x42/0x50 fs/namei.c:4182
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #1 (&ovl_i_mutex_key[depth]){+.+.}:
down_write+0x93/0x150 kernel/locking/rwsem.c:1531
inode_lock include/linux/fs.h:791 [inline]
process_measurement+0x6f7/0x1850 security/integrity/ima/ima_main.c:230
ima_file_check+0xc5/0x110 security/integrity/ima/ima_main.c:442
do_last fs/namei.c:3494 [inline]
path_openat+0x1347/0x33f0 fs/namei.c:3607
do_filp_open+0x192/0x260 fs/namei.c:3637
do_open_execat+0x13b/0x6d0 fs/exec.c:860
__do_execve_file.isra.0+0x16d5/0x2270 fs/exec.c:1791
do_execveat_common fs/exec.c:1897 [inline]
do_execve fs/exec.c:1914 [inline]
__do_sys_execve fs/exec.c:1990 [inline]
__se_sys_execve fs/exec.c:1985 [inline]
__x64_sys_execve+0x8f/0xc0 fs/exec.c:1985
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:2481 [inline]
check_prevs_add kernel/locking/lockdep.c:2586 [inline]
validate_chain kernel/locking/lockdep.c:3203 [inline]
__lock_acquire+0x29cd/0x6320 kernel/locking/lockdep.c:4190
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4720
__mutex_lock_common kernel/locking/mutex.c:956 [inline]
__mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1103
mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1133
lock_trace+0x4a/0xe0 fs/proc/base.c:408
proc_pid_stack+0xbf/0x200 fs/proc/base.c:452
proc_single_show+0xfd/0x1c0 fs/proc/base.c:758
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:1053
do_preadv+0x1c4/0x280 fs/read_write.c:1145
__do_sys_preadv fs/read_write.c:1195 [inline]
__se_sys_preadv fs/read_write.c:1190 [inline]
__x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1190
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.1/12868:
#0: ffff8880a96aff40 (&p->lock){+.+.}, at: seq_read+0x71/0x1170 fs/seq_file.c:161
stack backtrace:
CPU: 0 PID: 12868 Comm: syz-executor.1 Not tainted 5.6.0-rc2-next-20200218-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:1688
check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1812
check_prev_add kernel/locking/lockdep.c:2481 [inline]
check_prevs_add kernel/locking/lockdep.c:2586 [inline]
validate_chain kernel/locking/lockdep.c:3203 [inline]
__lock_acquire+0x29cd/0x6320 kernel/locking/lockdep.c:4190
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4720
__mutex_lock_common kernel/locking/mutex.c:956 [inline]
__mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1103
mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1133
lock_trace+0x4a/0xe0 fs/proc/base.c:408
proc_pid_stack+0xbf/0x200 fs/proc/base.c:452
proc_single_show+0xfd/0x1c0 fs/proc/base.c:758
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:1053
do_preadv+0x1c4/0x280 fs/read_write.c:1145
__do_sys_preadv fs/read_write.c:1195 [inline]
__se_sys_preadv fs/read_write.c:1190 [inline]
__x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1190
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c449
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:00007f545089ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007f545089f6d4 RCX: 000000000045c449
RDX: 000000000000022a RSI: 00000000200017c0 RDI: 0000000000000004
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000856 R14: 00000000004cad5b R15: 000000000076bf2c