======================================================
WARNING: possible circular locking dependency detected
4.14.104+ #22 Not tainted
------------------------------------------------------
syz-executor.3/2443 is trying to acquire lock:
(&sig->cred_guard_mutex){+.+.}, at: [<ffffffff97e9d6ea>] do_io_accounting+0x1da/0x790 fs/proc/base.c:2727
but task is already holding lock:
(&p->lock){+.+.}, at: [<ffffffff97dce06d>] seq_read+0xcd/0x1180 fs/seq_file.c:165
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&p->lock){+.+.}:
-> #1 (&pipe->mutex/1){+.+.}:
-> #0 (&sig->cred_guard_mutex){+.+.}:
other info that might help us debug this:
Chain exists of:
&sig->cred_guard_mutex --> &pipe->mutex/1 --> &p->lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&p->lock);
lock(&pipe->mutex/1);
lock(&p->lock);
lock(&sig->cred_guard_mutex);
*** DEADLOCK ***
1 lock held by syz-executor.3/2443:
#0: (&p->lock){+.+.}, at: [<ffffffff97dce06d>] seq_read+0xcd/0x1180 fs/seq_file.c:165
stack backtrace:
CPU: 0 PID: 2443 Comm: syz-executor.3 Not tainted 4.14.104+ #22
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x10e lib/dump_stack.c:53
print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258