netdev - [PATCH bpf] samples/bpf: Fix Segmentation fault for xdp

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Date:   Wed, 16 Jun 2021 12:23:24 +0800
From:   Wang Hai <wanghai38@...wei.com>
To:     <davem@...emloft.net>, <kuba@...nel.org>, <ast@...nel.org>,
        <daniel@...earbox.net>, <hawk@...nel.org>,
        <john.fastabend@...il.com>, <andrii@...nel.org>, <kafai@...com>,
        <songliubraving@...com>, <yhs@...com>, <kpsingh@...nel.org>
CC:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH bpf] samples/bpf: Fix Segmentation fault for xdp_redirect command

A Segmentation fault error is caused when the following command
is executed.

$ sudo ./samples/bpf/xdp_redirect lo
Segmentation fault

This command is missing a device <IFNAME|IFINDEX> as an argument, resulting
in out-of-bounds access from argv.

If the number of devices for the xdp_redirect parameter is not 2,
we should report an error and exit.

Fixes: 24251c264798 ("samples/bpf: add option for native and skb mode for redirect apps")
Signed-off-by: Wang Hai <wanghai38@...wei.com>
---
 samples/bpf/xdp_redirect_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/xdp_redirect_user.c b/samples/bpf/xdp_redirect_user.c
index c903f1ccc15e..93854e135134 100644
--- a/samples/bpf/xdp_redirect_user.c
+++ b/samples/bpf/xdp_redirect_user.c
@@ -130,7 +130,7 @@ int main(int argc, char **argv)
 	if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
 		xdp_flags |= XDP_FLAGS_DRV_MODE;
 
-	if (optind == argc) {
+	if (optind + 2 != argc) {
 		printf("usage: %s <IFNAME|IFINDEX>_IN <IFNAME|IFINDEX>_OUT\n", argv[0]);
 		return 1;
 	}
-- 
2.17.1