============================================ WARNING: possible recursive locking detected 4.13.0-rc7-next-20170829+ #11 Not tainted -------------------------------------------- syz-executor0/4472 is trying to acquire lock: (sk_lock-AF_KCM){+.+.}, at: [] lock_sock include/net/sock.h:1459 [inline] (sk_lock-AF_KCM){+.+.}, at: [] kcm_sendpage+0x16e/0x1880 net/kcm/kcmsock.c:774 but task is already holding lock: (sk_lock-AF_KCM){+.+.}, at: [] lock_sock include/net/sock.h:1459 [inline] (sk_lock-AF_KCM){+.+.}, at: [] kcm_sendmsg+0x1ec/0x2200 net/kcm/kcmsock.c:910 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(sk_lock-AF_KCM); lock(sk_lock-AF_KCM); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by syz-executor0/4472: #0: (sk_lock-AF_KCM){+.+.}, at: [] lock_sock include/net/sock.h:1459 [inline] #0: (sk_lock-AF_KCM){+.+.}, at: [] kcm_sendmsg+0x1ec/0x2200 net/kcm/kcmsock.c:910 stack backtrace: CPU: 0 PID: 4472 Comm: syz-executor0 Not tainted 4.13.0-rc7-next-20170829+ #11 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 print_deadlock_bug kernel/locking/lockdep.c:1797 [inline] check_deadlock kernel/locking/lockdep.c:1844 [inline] validate_chain kernel/locking/lockdep.c:2453 [inline] __lock_acquire+0x1232/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 lock_sock_nested+0xc2/0x110 net/core/sock.c:2772 lock_sock include/net/sock.h:1459 [inline] kcm_sendpage+0x16e/0x1880 net/kcm/kcmsock.c:774 kernel_sendpage+0x8d/0xe0 net/socket.c:3387 kcm_write_msgs+0x404/0x1b80 net/kcm/kcmsock.c:646 kcm_sendmsg+0x1446/0x2200 net/kcm/kcmsock.c:1035 sock_sendmsg_nosec net/socket.c:633 [inline] sock_sendmsg+0xca/0x110 net/socket.c:643 sock_write_iter+0x320/0x5e0 net/socket.c:912 call_write_iter include/linux/fs.h:1744 [inline] new_sync_write fs/read_write.c:457 [inline] __vfs_write+0x68a/0x970 fs/read_write.c:470 vfs_write+0x18f/0x510 fs/read_write.c:518 SYSC_write fs/read_write.c:565 [inline] SyS_write+0xef/0x220 fs/read_write.c:557 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x451e59 RSP: 002b:00007f3b46a99c08 EFLAGS: 00000216 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 0000000000451e59 RDX: 000000000000009a RSI: 0000000020ef4000 RDI: 0000000000000008 RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004b70e7 R13: 00000000ffffffff R14: 0000000000000005 R15: 0000000020b4cfd0