linux-kernel - [PATCH bpf-next] samples/bpf: xdp_router_ipv4

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Date:   Tue, 22 Nov 2022 10:32:56 +0800
From:   Rong Tao <rtoax@...mail.com>
To:     ast@...nel.org
Cc:     Rong Tao <rongtao@...tc.cn>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        netdev@...r.kernel.org (open list:XDP (eXpress Data Path)),
        bpf@...r.kernel.org (open list:XDP (eXpress Data Path)),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH bpf-next] samples/bpf: xdp_router_ipv4_user: Fix write overflow

From: Rong Tao <rongtao@...tc.cn>

prefix_key->data allocates three bytes using alloca(), but four bytes are
accessed in the program.

Signed-off-by: Rong Tao <rongtao@...tc.cn>
---
 samples/bpf/xdp_router_ipv4_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/xdp_router_ipv4_user.c b/samples/bpf/xdp_router_ipv4_user.c
index 683913bbf279..9d41db09c480 100644
--- a/samples/bpf/xdp_router_ipv4_user.c
+++ b/samples/bpf/xdp_router_ipv4_user.c
@@ -162,7 +162,7 @@ static void read_route(struct nlmsghdr *nh, int nll)
 				__be32 gw;
 			} *prefix_value;
 
-			prefix_key = alloca(sizeof(*prefix_key) + 3);
+			prefix_key = alloca(sizeof(*prefix_key) + 4);
 			prefix_value = alloca(sizeof(*prefix_value));
 
 			prefix_key->prefixlen = 32;
-- 
2.38.1