audit: type=1400 audit(1560431785.190:36): avc: denied { map } for pid=7516 comm="syz-executor499" path="/root/syz-executor499006658" dev="sda1" ino=16483 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1 ====================================================== WARNING: possible circular locking dependency detected 4.19.50 #22 Not tainted ------------------------------------------------------ syz-executor499/7516 is trying to acquire lock: 0000000022e241f1 (&sig->cred_guard_mutex){+.+.}, at: do_io_accounting+0x1f4/0x830 fs/proc/base.c:2704 but task is already holding lock: 000000001d704e75 (&p->lock){+.+.}, at: seq_read+0x71/0x1110 fs/seq_file.c:161 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:925 [inline] __mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 seq_read+0x71/0x1110 fs/seq_file.c:161 do_loop_readv_writev fs/read_write.c:701 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_read+0x490/0x640 fs/read_write.c:925 vfs_readv+0xf0/0x160 fs/read_write.c:987 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x478/0x890 fs/splice.c:417 do_splice_to+0x127/0x180 fs/splice.c:881 splice_direct_to_actor+0x256/0x890 fs/splice.c:953 do_splice_direct+0x1da/0x2a0 fs/splice.c:1062 do_sendfile+0x597/0xce0 fs/read_write.c:1447 __do_sys_sendfile64 fs/read_write.c:1508 [inline] __se_sys_sendfile64 fs/read_write.c:1494 [inline] __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1494 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (sb_writers#4){.+.+}: 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+0x20b/0x360 fs/super.c:1387 sb_start_write include/linux/fs.h:1578 [inline] mnt_want_write+0x3f/0xc0 fs/namespace.c:360 ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:24 ovl_xattr_set+0x53/0x5b0 fs/overlayfs/inode.c:332 ovl_posix_acl_xattr_set+0x33a/0x9a0 fs/overlayfs/super.c:908 __vfs_setxattr+0x11f/0x180 fs/xattr.c:149 __vfs_setxattr_noperm+0x11c/0x410 fs/xattr.c:180 vfs_setxattr+0xda/0x100 fs/xattr.c:223 setxattr+0x26f/0x380 fs/xattr.c:450 path_setxattr+0x197/0x1b0 fs/xattr.c:469 __do_sys_setxattr fs/xattr.c:484 [inline] __se_sys_setxattr fs/xattr.c:480 [inline] __x64_sys_setxattr+0xc4/0x150 fs/xattr.c:480 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&ovl_i_mutex_dir_key[depth]){++++}: down_read+0x3b/0xb0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:757 [inline] do_last fs/namei.c:3323 [inline] path_openat+0x1e77/0x4690 fs/namei.c:3534 do_filp_open+0x1a1/0x280 fs/namei.c:3564 do_open_execat+0x140/0x660 fs/exec.c:853 __do_execve_file.isra.0+0x15a4/0x2150 fs/exec.c:1755 do_execveat_common fs/exec.c:1866 [inline] do_execveat fs/exec.c:1894 [inline] __do_sys_execveat fs/exec.c:1975 [inline] __se_sys_execveat fs/exec.c:1967 [inline] __x64_sys_execveat+0xed/0x130 fs/exec.c:1967 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3900 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 do_io_accounting+0x1f4/0x830 fs/proc/base.c:2704 proc_tid_io_accounting+0x20/0x30 fs/proc/base.c:2747 proc_single_show+0xf0/0x180 fs/proc/base.c:737 seq_read+0x4ca/0x1110 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:701 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_read+0x490/0x640 fs/read_write.c:925 vfs_readv+0xf0/0x160 fs/read_write.c:987 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x478/0x890 fs/splice.c:417 do_splice_to+0x127/0x180 fs/splice.c:881 splice_direct_to_actor+0x256/0x890 fs/splice.c:953 do_splice_direct+0x1da/0x2a0 fs/splice.c:1062 do_sendfile+0x597/0xce0 fs/read_write.c:1447 __do_sys_sendfile64 fs/read_write.c:1508 [inline] __se_sys_sendfile64 fs/read_write.c:1494 [inline] __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1494 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &sig->cred_guard_mutex --> sb_writers#4 --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock(sb_writers#4); lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 2 locks held by syz-executor499/7516: #0: 000000009e00f5b3 (sb_writers#4){.+.+}, at: file_start_write include/linux/fs.h:2773 [inline] #0: 000000009e00f5b3 (sb_writers#4){.+.+}, at: do_sendfile+0x9b9/0xce0 fs/read_write.c:1446 #1: 000000001d704e75 (&p->lock){+.+.}, at: seq_read+0x71/0x1110 fs/seq_file.c:161 stack backtrace: CPU: 0 PID: 7516 Comm: syz-executor499 Not tainted 4.19.50 #22 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1221 check_prev_add kernel/locking/lockdep.c:1861 [inline] check_prevs_add kernel/locking/lockdep.c:1974 [inline] validate_chain kernel/locking/lockdep.c:2415 [inline] __lock_acquire+0x2e6d/0x48f0 kernel/locking/lockdep.c:3411 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3900 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 do_io_accounting+0x1f4/0x830 fs/proc/base.c:2704 proc_tid_io_accounting+0x20/0x30 fs/proc/base.c:2747 proc_single_show+0xf0/0x180 fs/proc/base.c:737 seq_read+0x4ca/0x1110 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:701 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_read+0x490/0x640 fs/read_write.c:925 vfs_readv+0xf0/0x160 fs/read_write.c:987 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x478/0x890 fs/splice.c:417 do_splice_to+0x127/0x180 fs/splice.c:881 splice_direct_to_actor+0x256/0x890 fs/splice.c:953 do_splice_direct+0x1da/0x2a0 fs/splice.c:1062 do_sendfile+0x597/0xce0 fs/read_write.c:1447 __do_sys_sendfile64 fs/read_write.c:1508 [inline] __se_sys_sendfile64 fs/read_write.c:1494 [inline] __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1494 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x440489 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffe57ac8268 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000006f69 RCX: 0000000000440489 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005 RBP: 00000000006cb018 R08: 68742f636f72702f R09: 68742f