RDMA/rxe: Fix NULL-ptr-deref in rxe_qp_do_cleanup() when socket create failed

There is a null-ptr-deref when mount.cifs over rdma:

  BUG: KASAN: null-ptr-deref in rxe_qp_do_cleanup+0x2f3/0x360 [rdma_rxe]
  Read of size 8 at addr 0000000000000018 by task mount.cifs/3046

  CPU: 2 PID: 3046 Comm: mount.cifs Not tainted 6.1.0-rc5+ #62
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc3
  Call Trace:
   <TASK>
   dump_stack_lvl+0x34/0x44
   kasan_report+0xad/0x130
   rxe_qp_do_cleanup+0x2f3/0x360 [rdma_rxe]
   execute_in_process_context+0x25/0x90
   __rxe_cleanup+0x101/0x1d0 [rdma_rxe]
   rxe_create_qp+0x16a/0x180 [rdma_rxe]
   create_qp.part.0+0x27d/0x340
   ib_create_qp_kernel+0x73/0x160
   rdma_create_qp+0x100/0x230
   _smbd_get_connection+0x752/0x20f0
   smbd_get_connection+0x21/0x40
   cifs_get_tcp_session+0x8ef/0xda0
   mount_get_conns+0x60/0x750
   cifs_mount+0x103/0xd00
   cifs_smb3_do_mount+0x1dd/0xcb0
   smb3_get_tree+0x1d5/0x300
   vfs_get_tree+0x41/0xf0
   path_mount+0x9b3/0xdd0
   __x64_sys_mount+0x190/0x1d0
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x46/0xb0

The root cause of the issue is the socket create failed in
rxe_qp_init_req().

So move the reset rxe_qp_do_cleanup() after the NULL ptr check.

Fixes: 8700e3e7c4 ("Soft RoCE driver")
Link: https://lore.kernel.org/r/20221122151437.1057671-1-zhangxiaoxu5@huawei.com
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_qp.c

@@ -817,12 +817,12 @@ static void rxe_qp_do_cleanup(struct work_struct *work)
 	if (qp->resp.mr)
 		rxe_put(qp->resp.mr);
 
-	if (qp_type(qp) == IB_QPT_RC)
-		sk_dst_reset(qp->sk->sk);
-
 	free_rd_atomic_resources(qp);
 
 	if (qp->sk) {
+		if (qp_type(qp) == IB_QPT_RC)
+			sk_dst_reset(qp->sk->sk);
+
 		kernel_sock_shutdown(qp->sk, SHUT_RDWR);
 		sock_release(qp->sk);
 	}