====================================================== WARNING: possible circular locking dependency detected 4.14.246-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor709/7976 is trying to acquire lock: (&sig->cred_guard_mutex){+.+.}, at: [] lock_trace fs/proc/base.c:407 [inline] (&sig->cred_guard_mutex){+.+.}, at: [] proc_pid_personality+0x48/0x160 fs/proc/base.c:2926 but task is already holding lock: (&p->lock){+.+.}, at: [] seq_read+0xba/0x1180 fs/seq_file.c:168 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+0xc4/0x1310 kernel/locking/mutex.c:893 seq_read+0xba/0x1180 fs/seq_file.c:168 proc_reg_read+0xee/0x1a0 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+0x3eb/0x5b0 fs/read_write.c:919 vfs_readv+0xc8/0x120 fs/read_write.c:981 kernel_readv fs/splice.c:361 [inline] default_file_splice_read+0x418/0x910 fs/splice.c:416 do_splice_to+0xfb/0x140 fs/splice.c:880 splice_direct_to_actor+0x207/0x730 fs/splice.c:952 do_splice_direct+0x164/0x210 fs/splice.c:1061 do_sendfile+0x47f/0xb30 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+0x46/0xbb -> #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+0x64/0x260 fs/super.c:1342 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+0x77a/0x1750 fs/namei.c:3241 do_last fs/namei.c:3334 [inline] path_openat+0xe08/0x2970 fs/namei.c:3569 do_filp_open+0x179/0x3c0 fs/namei.c:3603 do_sys_open+0x296/0x410 fs/open.c:1081 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #1 (&ovl_i_mutex_dir_key[depth]){++++}: down_read+0x36/0x80 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:729 [inline] do_last fs/namei.c:3333 [inline] path_openat+0x149b/0x2970 fs/namei.c:3569 do_filp_open+0x179/0x3c0 fs/namei.c:3603 do_open_execat+0xd3/0x450 fs/exec.c:849 do_execveat_common+0x711/0x1f30 fs/exec.c:1755 do_execve fs/exec.c:1860 [inline] SYSC_execve fs/exec.c:1941 [inline] SyS_execve+0x3b/0x50 fs/exec.c:1936 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #0 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893 lock_trace fs/proc/base.c:407 [inline] proc_pid_personality+0x48/0x160 fs/proc/base.c:2926 proc_single_show+0xe7/0x150 fs/proc/base.c:761 seq_read+0x4e4/0x1180 fs/seq_file.c:240 __vfs_read+0xe4/0x620 fs/read_write.c:411 vfs_read+0x139/0x340 fs/read_write.c:447 SYSC_read fs/read_write.c:574 [inline] SyS_read+0xf2/0x210 fs/read_write.c:567 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb 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-executor709/7976: #0: (&p->lock){+.+.}, at: [] seq_read+0xba/0x1180 fs/seq_file.c:168 stack backtrace: CPU: 1 PID: 7976 Comm: syz-executor709 Not tainted 4.14.246-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+0x1b2/0x281 lib/dump_stack.c:58 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1258 check_prev_add kernel/locking/lockdep.c:1905 [inline] check_prevs_add kernel/locking/lockdep.c:2022 [inline] validate_chain kernel/locking/lockdep.c:2464 [inline] __lock_acquire+0x2e0e/0x3f20 kernel/locking/lockdep.c:3491 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893 lock_trace fs/proc/base.c:407 [inline] proc_pid_personality+0x48/0x160 fs/proc/base.c:2926 proc_single_show+0xe7/0x150 fs/proc/base.c:761 seq_read+0x4e4/0x1180 fs/seq_file.c:240 __vfs_read+0xe4/0x620 fs/read_write.c:411 vfs_read+0x139/0x340 fs/read_write.c:447 SYSC_read fs/read_write.c:574 [inline] SyS_read+0xf2/0x210 fs/read_write.c:567 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x43f299 RSP: 002b:00007ffda5734c08 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043f299 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005 RBP: 00007ffda5734c