bpf: Initialise retval in bpf_prog_test_run_xdp()

The kernel test robot pointed out that the newly added
bpf_test_run_xdp_live() runner doesn't set the retval in the caller (by
design), which means that the variable can be passed unitialised to
bpf_test_finish(). Fix this by initialising the variable properly.

Fixes: b530e9e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RUN")
Reported-by: kernel test robot <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: tohojo

net/bpf/test_run.c

@@ -1207,9 +1207,9 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 	bool do_live = (kattr->test.flags & BPF_F_TEST_XDP_LIVE_FRAMES);
 	u32 tailroom = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 	u32 batch_size = kattr->test.batch_size;
+	u32 retval = 0, duration, max_data_sz;
 	u32 size = kattr->test.data_size_in;
 	u32 headroom = XDP_PACKET_HEADROOM;
-	u32 retval, duration, max_data_sz;
 	u32 repeat = kattr->test.repeat;
 	struct netdev_rx_queue *rxqueue;
 	struct skb_shared_info *sinfo;