====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc7-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.1/25454 is trying to acquire lock: ffff88809008cd00 (&p->lock){+.+.}, at: seq_read+0x66/0xd20 fs/seq_file.c:161 but task is already holding lock: ffff88809963a428 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2904 [inline] ffff88809963a428 (sb_writers#3){.+.+}, at: do_sendfile+0x7d7/0xfd0 fs/read_write.c:1519 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (sb_writers#3){.+.+}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 percpu_down_read include/linux/percpu-rwsem.h:40 [inline] __sb_start_write+0x184/0x400 fs/super.c:1674 sb_start_write include/linux/fs.h:1650 [inline] mnt_want_write+0x45/0x90 fs/namespace.c:354 ovl_xattr_set+0x60/0x3f0 fs/overlayfs/inode.c:324 ovl_posix_acl_xattr_set+0x3c4/0x7a0 fs/overlayfs/super.c:911 __vfs_removexattr+0x3b9/0x3f0 fs/xattr.c:377 vfs_removexattr+0xa5/0x1c0 fs/xattr.c:396 removexattr fs/xattr.c:691 [inline] path_removexattr+0x174/0x240 fs/xattr.c:705 __do_sys_lremovexattr fs/xattr.c:725 [inline] __se_sys_lremovexattr fs/xattr.c:722 [inline] __x64_sys_lremovexattr+0x59/0x70 fs/xattr.c:722 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&ovl_i_mutex_dir_key[depth]#2){++++}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 down_read+0x36/0x50 kernel/locking/rwsem.c:1495 inode_lock_shared include/linux/fs.h:802 [inline] do_last fs/namei.c:3400 [inline] path_openat+0xbe2/0x40d0 fs/namei.c:3607 do_filp_open+0x191/0x3a0 fs/namei.c:3637 do_open_execat+0x101/0x5f0 fs/exec.c:860 __do_execve_file+0x6ea/0x1b80 fs/exec.c:1765 do_execveat_common fs/exec.c:1871 [inline] do_execve fs/exec.c:1888 [inline] __do_sys_execve fs/exec.c:1964 [inline] __se_sys_execve fs/exec.c:1959 [inline] __x64_sys_execve+0x90/0xa0 fs/exec.c:1959 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __mutex_lock_common+0x189/0x2fc0 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_killable_nested+0x1a/0x20 kernel/locking/mutex.c:1133 do_io_accounting fs/proc/base.c:2864 [inline] proc_tgid_io_accounting+0x163/0x570 fs/proc/base.c:2913 proc_single_show+0xd5/0x160 fs/proc/base.c:758 seq_read+0x4aa/0xd20 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x43b/0x550 fs/read_write.c:935 vfs_readv+0xc2/0x120 fs/read_write.c:1053 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:422 do_splice_to fs/splice.c:892 [inline] splice_direct_to_actor+0x3c1/0xb40 fs/splice.c:971 do_splice_direct+0x1fb/0x330 fs/splice.c:1080 do_sendfile+0x803/0xfd0 fs/read_write.c:1520 __do_sys_sendfile64 fs/read_write.c:1581 [inline] __se_sys_sendfile64 fs/read_write.c:1567 [inline] __x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1567 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&p->lock){+.+.}: check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __mutex_lock_common+0x189/0x2fc0 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1118 seq_read+0x66/0xd20 fs/seq_file.c:161 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x43b/0x550 fs/read_write.c:935 vfs_readv+0xc2/0x120 fs/read_write.c:1053 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:422 do_splice_to fs/splice.c:892 [inline] splice_direct_to_actor+0x3c1/0xb40 fs/splice.c:971 do_splice_direct+0x1fb/0x330 fs/splice.c:1080 do_sendfile+0x803/0xfd0 fs/read_write.c:1520 __do_sys_sendfile64 fs/read_write.c:1581 [inline] __se_sys_sendfile64 fs/read_write.c:1567 [inline] __x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1567 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &p->lock --> &ovl_i_mutex_dir_key[depth]#2 --> sb_writers#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sb_writers#3); lock(&ovl_i_mutex_dir_key[depth]#2); lock(sb_writers#3); lock(&p->lock); *** DEADLOCK *** 1 lock held by syz-executor.1/25454: #0: ffff88809963a428 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2904 [inline] #0: ffff88809963a428 (sb_writers#3){.+.+}, at: do_sendfile+0x7d7/0xfd0 fs/read_write.c:1519 stack backtrace: CPU: 1 PID: 25454 Comm: syz-executor.1 Not tainted 5.6.0-rc7-syzkaller #0 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+0x1e9/0x30e lib/dump_stack.c:118 print_circular_bug+0xc3f/0xe70 kernel/locking/lockdep.c:1684 check_noncircular+0x1fb/0x3a0 kernel/locking/lockdep.c:1808 check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __mutex_lock_common+0x189/0x2fc0 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1118 seq_read+0x66/0xd20 fs/seq_file.c:161 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x43b/0x550 fs/read_write.c:935 vfs_readv+0xc2/0x120 fs/read_write.c:1053 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:422 do_splice_to fs/splice.c:892 [inline] splice_direct_to_actor+0x3c1/0xb40 fs/splice.c:971 do_splice_direct+0x1fb/0x330 fs/splice.c:1080 do_sendfile+0x803/0xfd0 fs/read_write.c:1520 __do_sys_sendfile64 fs/read_write.c:1581 [inline] __se_sys_sendfile64 fs/read_write.c:1567 [inline] __x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1567 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45c849 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f1a384d9c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f1a384da6d4 RCX: 000000000045c849 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005 RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 000000000000003b R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000008d0 R14: 00000000004cb74a R15: 000000000076bf0c