====================================================== WARNING: possible circular locking dependency detected 4.14.175-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.3/11974 is trying to acquire lock: (&sig->cred_guard_mutex){+.+.}, at: [] do_io_accounting+0x1c7/0x750 fs/proc/base.c:2726 but task is already holding lock: (&p->lock){+.+.}, at: [] seq_read+0xba/0x1160 fs/seq_file.c:165 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:756 [inline] __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893 seq_read+0xba/0x1160 fs/seq_file.c:165 proc_reg_read+0xf2/0x160 fs/proc/inode.c:217 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e3/0x5a0 fs/read_write.c:919 vfs_readv+0xd3/0x130 fs/read_write.c:981 kernel_readv fs/splice.c:361 [inline] default_file_splice_read+0x41d/0x870 fs/splice.c:416 do_splice_to+0xfb/0x150 fs/splice.c:880 splice_direct_to_actor+0x20a/0x730 fs/splice.c:952 do_splice_direct+0x164/0x210 fs/splice.c:1061 do_sendfile+0x469/0xaf0 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1502 [inline] SyS_sendfile64+0xff/0x110 fs/read_write.c:1488 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 -> #2 (sb_writers#3){.+.+}: percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline] percpu_down_read include/linux/percpu-rwsem.h:59 [inline] __sb_start_write+0x1a1/0x2e0 fs/super.c:1363 sb_start_write include/linux/fs.h:1549 [inline] mnt_want_write+0x3a/0xb0 fs/namespace.c:386 ovl_create_object+0x75/0x1d0 fs/overlayfs/dir.c:538 lookup_open+0x10e8/0x1750 fs/namei.c:3241 do_last fs/namei.c:3334 [inline] path_openat+0xfc1/0x3c50 fs/namei.c:3569 do_filp_open+0x18e/0x250 fs/namei.c:3603 do_sys_open+0x29d/0x3f0 fs/open.c:1081 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 -> #1 (&ovl_i_mutex_dir_key[depth]){++++}: down_read+0x37/0xa0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:729 [inline] do_last fs/namei.c:3333 [inline] path_openat+0x185a/0x3c50 fs/namei.c:3569 do_filp_open+0x18e/0x250 fs/namei.c:3603 do_open_execat+0xda/0x430 fs/exec.c:849 do_execveat_common.isra.0+0x694/0x1c70 fs/exec.c:1740 do_execve fs/exec.c:1847 [inline] SYSC_execve fs/exec.c:1928 [inline] SyS_execve+0x34/0x40 fs/exec.c:1923 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 -> #0 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3994 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893 do_io_accounting+0x1c7/0x750 fs/proc/base.c:2726 proc_single_show+0xe7/0x150 fs/proc/base.c:761 seq_read+0x4d2/0x1160 fs/seq_file.c:237 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e3/0x5a0 fs/read_write.c:919 vfs_readv+0xd3/0x130 fs/read_write.c:981 do_preadv+0x161/0x200 fs/read_write.c:1065 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 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.3/11974: #0: (&p->lock){+.+.}, at: [] seq_read+0xba/0x1160 fs/seq_file.c:165 stack backtrace: CPU: 0 PID: 11974 Comm: syz-executor.3 Not tainted 4.14.175-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x13e/0x194 lib/dump_stack.c:58 print_circular_bug.isra.0.cold+0x1c4/0x282 kernel/locking/lockdep.c:1258 check_prev_add kernel/locking/lockdep.c:1901 [inline] check_prevs_add kernel/locking/lockdep.c:2018 [inline] validate_chain kernel/locking/lockdep.c:2460 [inline] __lock_acquire+0x2cb3/0x4620 kernel/locking/lockdep.c:3487 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3994 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893 do_io_accounting+0x1c7/0x750 fs/proc/base.c:2726 proc_single_show+0xe7/0x150 fs/proc/base.c:761 seq_read+0x4d2/0x1160 fs/seq_file.c:237 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e3/0x5a0 fs/read_write.c:919 vfs_readv+0xd3/0x130 fs/read_write.c:981 do_preadv+0x161/0x200 fs/read_write.c:1065 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c889 RSP: 002b:00007fca93789c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127 RAX: ffffffffffffffda RBX: 00007fca9378a6d4 RCX: 000000000045c889 RDX: 0000000000000232 RSI: 0000000020000480 RDI: 0000000000000005 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000085a R14: 00000000004cb1ec R15: 000000000076bf0c audit: type=1804 audit(1586487736.432:43): pid=11958 uid=0 auid=0 ses=4 subj=system_u:system_r:kernel_t:s0 op="invalid_pcr" cause="ToMToU" comm="syz-executor.2" name="/root/syzkaller-testdir172092852/syzkaller.8DYXwA/109/cgroup.controllers" dev="sda1" ino=16100 res=1 audit: type=1400 audit(1586487736.702:44): avc: denied { name_connect } for pid=11990 comm="syz-executor.2" scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:port_t:s0 tclass=dccp_socket permissive=1 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12009 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12009 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12009 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12009 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12009 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12054 comm=syz-executor.3 overlayfs: filesystem on './file0' not supported as upperdir SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12054 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12054 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12054 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12054 comm=syz-executor.3 netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. selinux_nlmsg_perm: 20 callbacks suppressed SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12311 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12311 comm=syz-executor.3 netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12311 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12311 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12311 comm=syz-executor.3 netlink: 20 bytes leftover after parsing attributes in process `syz-executor.5'. SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12356 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12356 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12356 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12356 comm=syz-executor.3 SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=12356 comm=syz-executor.3