====================================================== WARNING: possible circular locking dependency detected 4.14.104+ #21 Not tainted ------------------------------------------------------ syz-executor.3/2241 is trying to acquire lock: (&sig->cred_guard_mutex){+.+.}, at: [] do_io_accounting+0x1da/0x790 fs/proc/base.c:2727 but task is already holding lock: (&p->lock){+.+.}, at: [] 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.3/2241: #0: (&p->lock){+.+.}, at: [] seq_read+0xcd/0x1180 fs/seq_file.c:165 stack backtrace: CPU: 0 PID: 2241 Comm: syz-executor.3 Not tainted 4.14.104+ #21 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 selinux_nlmsg_perm: 24 callbacks suppressed SELinux: unrecognized netlink message: protocol=0 nlmsg_type=29231 sclass=netlink_route_socket pig=2308 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=12340 sclass=netlink_route_socket pig=2308 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=12336 sclass=netlink_route_socket pig=2308 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=28208 sclass=netlink_route_socket pig=2329 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=23606 sclass=netlink_route_socket pig=2329 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=29231 sclass=netlink_route_socket pig=2339 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=29231 sclass=netlink_route_socket pig=2391 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=12340 sclass=netlink_route_socket pig=2391 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=12336 sclass=netlink_route_socket pig=2391 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=12338 sclass=netlink_route_socket pig=2401 comm=syz-executor.0 selinux_nlmsg_perm: 30 callbacks suppressed SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=2786 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=65535 sclass=netlink_route_socket pig=2797 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=29231 sclass=netlink_route_socket pig=2786 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=2797 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=65535 sclass=netlink_route_socket pig=2797 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=11890 sclass=netlink_route_socket pig=2797 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=29231 sclass=netlink_route_socket pig=2836 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=11890 sclass=netlink_route_socket pig=2843 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=29231 sclass=netlink_route_socket pig=2859 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=11890 sclass=netlink_route_socket pig=2870 comm=syz-executor.0