====================================================== WARNING: possible circular locking dependency detected 4.14.218-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.2/22266 is trying to acquire lock: (&ovl_i_mutex_dir_key[depth]){++++}, at: [] inode_lock_shared syzkaller/managers/linux-4-14/kernel/./include/linux/fs.h:729 [inline] (&ovl_i_mutex_dir_key[depth]){++++}, at: [] do_last syzkaller/managers/linux-4-14/kernel/fs/namei.c:3333 [inline] (&ovl_i_mutex_dir_key[depth]){++++}, at: [] path_openat+0x149b/0x2970 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3569 but task is already holding lock: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds syzkaller/managers/linux-4-14/kernel/fs/exec.c:1404 [inline] (&sig->cred_guard_mutex){+.+.}, at: [] do_execveat_common+0x319/0x1f30 syzkaller/managers/linux-4-14/kernel/fs/exec.c:1748 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&sig->cred_guard_mutex){+.+.}: __mutex_lock_common syzkaller/managers/linux-4-14/kernel/kernel/locking/mutex.c:756 [inline] __mutex_lock+0xc4/0x1310 syzkaller/managers/linux-4-14/kernel/kernel/locking/mutex.c:893 lock_trace syzkaller/managers/linux-4-14/kernel/fs/proc/base.c:407 [inline] proc_pid_syscall+0xa7/0x2a0 syzkaller/managers/linux-4-14/kernel/fs/proc/base.c:639 proc_single_show+0xe7/0x150 syzkaller/managers/linux-4-14/kernel/fs/proc/base.c:761 seq_read+0x4cf/0x1120 syzkaller/managers/linux-4-14/kernel/fs/seq_file.c:237 do_loop_readv_writev syzkaller/managers/linux-4-14/kernel/fs/read_write.c:695 [inline] do_loop_readv_writev syzkaller/managers/linux-4-14/kernel/fs/read_write.c:682 [inline] do_iter_read+0x3eb/0x5b0 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:919 vfs_readv+0xc8/0x120 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:981 do_preadv syzkaller/managers/linux-4-14/kernel/fs/read_write.c:1065 [inline] SYSC_preadv syzkaller/managers/linux-4-14/kernel/fs/read_write.c:1115 [inline] SyS_preadv+0x15a/0x200 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:1110 do_syscall_64+0x1d5/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #2 (&p->lock){+.+.}: __mutex_lock_common syzkaller/managers/linux-4-14/kernel/kernel/locking/mutex.c:756 [inline] __mutex_lock+0xc4/0x1310 syzkaller/managers/linux-4-14/kernel/kernel/locking/mutex.c:893 seq_read+0xba/0x1120 syzkaller/managers/linux-4-14/kernel/fs/seq_file.c:165 proc_reg_read+0xee/0x1a0 syzkaller/managers/linux-4-14/kernel/fs/proc/inode.c:217 do_loop_readv_writev syzkaller/managers/linux-4-14/kernel/fs/read_write.c:695 [inline] do_loop_readv_writev syzkaller/managers/linux-4-14/kernel/fs/read_write.c:682 [inline] do_iter_read+0x3eb/0x5b0 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:919 vfs_readv+0xc8/0x120 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:981 kernel_readv syzkaller/managers/linux-4-14/kernel/fs/splice.c:361 [inline] default_file_splice_read+0x418/0x910 syzkaller/managers/linux-4-14/kernel/fs/splice.c:416 do_splice_to+0xfb/0x140 syzkaller/managers/linux-4-14/kernel/fs/splice.c:880 splice_direct_to_actor+0x207/0x730 syzkaller/managers/linux-4-14/kernel/fs/splice.c:952 do_splice_direct+0x164/0x210 syzkaller/managers/linux-4-14/kernel/fs/splice.c:1061 do_sendfile+0x47f/0xb30 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:1441 SYSC_sendfile64 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:1502 [inline] SyS_sendfile64+0xff/0x110 syzkaller/managers/linux-4-14/kernel/fs/read_write.c:1488 do_syscall_64+0x1d5/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #1 (sb_writers#3){.+.+}: percpu_down_read_preempt_disable syzkaller/managers/linux-4-14/kernel/./include/linux/percpu-rwsem.h:36 [inline] percpu_down_read syzkaller/managers/linux-4-14/kernel/./include/linux/percpu-rwsem.h:59 [inline] __sb_start_write+0x64/0x260 syzkaller/managers/linux-4-14/kernel/fs/super.c:1342 sb_start_write syzkaller/managers/linux-4-14/kernel/./include/linux/fs.h:1549 [inline] mnt_want_write+0x3a/0xb0 syzkaller/managers/linux-4-14/kernel/fs/namespace.c:386 ovl_create_object+0x75/0x1d0 syzkaller/managers/linux-4-14/kernel/fs/overlayfs/dir.c:538 lookup_open+0x77a/0x1750 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3241 do_last syzkaller/managers/linux-4-14/kernel/fs/namei.c:3334 [inline] path_openat+0xe08/0x2970 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3569 do_filp_open+0x179/0x3c0 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3603 do_sys_open+0x296/0x410 syzkaller/managers/linux-4-14/kernel/fs/open.c:1081 do_syscall_64+0x1d5/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #0 (&ovl_i_mutex_dir_key[depth]){++++}: lock_acquire+0x170/0x3f0 syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:3998 down_read+0x36/0x80 syzkaller/managers/linux-4-14/kernel/kernel/locking/rwsem.c:24 inode_lock_shared syzkaller/managers/linux-4-14/kernel/./include/linux/fs.h:729 [inline] do_last syzkaller/managers/linux-4-14/kernel/fs/namei.c:3333 [inline] path_openat+0x149b/0x2970 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3569 do_filp_open+0x179/0x3c0 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3603 do_open_execat+0xd3/0x450 syzkaller/managers/linux-4-14/kernel/fs/exec.c:849 do_execveat_common+0x711/0x1f30 syzkaller/managers/linux-4-14/kernel/fs/exec.c:1755 do_execve syzkaller/managers/linux-4-14/kernel/fs/exec.c:1860 [inline] SYSC_execve syzkaller/managers/linux-4-14/kernel/fs/exec.c:1941 [inline] SyS_execve+0x3b/0x50 syzkaller/managers/linux-4-14/kernel/fs/exec.c:1936 do_syscall_64+0x1d5/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb other info that might help us debug this: Chain exists of: &ovl_i_mutex_dir_key[depth] --> &p->lock --> &sig->cred_guard_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sig->cred_guard_mutex); lock(&p->lock); lock(&sig->cred_guard_mutex); lock(&ovl_i_mutex_dir_key[depth]); *** DEADLOCK *** 1 lock held by syz-executor.2/22266: #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds syzkaller/managers/linux-4-14/kernel/fs/exec.c:1404 [inline] #0: (&sig->cred_guard_mutex){+.+.}, at: [] do_execveat_common+0x319/0x1f30 syzkaller/managers/linux-4-14/kernel/fs/exec.c:1748 stack backtrace: CPU: 1 PID: 22266 Comm: syz-executor.2 Not tainted 4.14.218-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack syzkaller/managers/linux-4-14/kernel/lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x281 syzkaller/managers/linux-4-14/kernel/lib/dump_stack.c:58 print_circular_bug.constprop.0.cold+0x2d7/0x41e syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:1258 check_prev_add syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:1905 [inline] check_prevs_add syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:2022 [inline] validate_chain syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:2464 [inline] __lock_acquire+0x2e0e/0x3f20 syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:3491 lock_acquire+0x170/0x3f0 syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:3998 down_read+0x36/0x80 syzkaller/managers/linux-4-14/kernel/kernel/locking/rwsem.c:24 inode_lock_shared syzkaller/managers/linux-4-14/kernel/./include/linux/fs.h:729 [inline] do_last syzkaller/managers/linux-4-14/kernel/fs/namei.c:3333 [inline] path_openat+0x149b/0x2970 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3569 do_filp_open+0x179/0x3c0 syzkaller/managers/linux-4-14/kernel/fs/namei.c:3603 do_open_execat+0xd3/0x450 syzkaller/managers/linux-4-14/kernel/fs/exec.c:849 do_execveat_common+0x711/0x1f30 syzkaller/managers/linux-4-14/kernel/fs/exec.c:1755 do_execve syzkaller/managers/linux-4-14/kernel/fs/exec.c:1860 [inline] SYSC_execve syzkaller/managers/linux-4-14/kernel/fs/exec.c:1941 [inline] SyS_execve+0x3b/0x50 syzkaller/managers/linux-4-14/kernel/fs/exec.c:1936 do_syscall_64+0x1d5/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x465d99 RSP: 002b:00007f75e1a43188 EFLAGS: 00000246 ORIG_RAX: 000000000000003b RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465d99 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000780 RBP: 00000000004bcf27 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007fff278f4f2f R14: 00007f75e1a43300 R15: 0000000000022000 overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.