syzbot

witness: lock order reversal:
 1st 0xffff8000011900e0 sbufrcv (&so->so_rcv.sb_lock)
 2nd 0xfffffd807bcb8e68 inode (&ip->i_lock)
lock order [1] sbufrcv (&so->so_rcv.sb_lock) -> [2] inode (&ip->i_lock)
lock order data 0xffffffff830d5171 -> 0xffffffff8304f7ef is missing
lock order [2] inode (&ip->i_lock) -> [1] sbufrcv (&so->so_rcv.sb_lock)
#0  rw_enter+0x122
#1  sblock+0xb7 sys/kern/uipc_socket2.c:549
#2  soreceive+0x298 sys/kern/uipc_socket.c:877
#3  fifo_read+0x11a sys/miscfs/fifofs/fifo_vnops.c:264
#4  VOP_READ+0x102 sys/kern/vfs_vops.c:227
#5  vn_rdwr+0x15b
#6  vndsetcred+0xa1 sys/dev/vnd.c:684
#7  vndioctl+0xe6c sys/dev/vnd.c:485
#8  VOP_IOCTL+0xac sys/kern/vfs_vops.c:264
#9  vn_ioctl+0xf6 sys/kern/vfs_vnops.c:525
#10 sys_ioctl+0x67c
#11 syscall+0xbb6 mi_syscall sys/sys/syscall_mi.h:179 [inline]
#11 syscall+0xbb6 sys/arch/amd64/amd64/trap.c:577
#12 Xsyscall+0x128
Stopped at      db_enter+0x25:  addq    $0x8,%rsp