netdev - [PATCH 9/9] udpv6: Check address length before reading address family

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Message-Id: <1555066599-9698-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
Date:   Fri, 12 Apr 2019 19:56:39 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [PATCH 9/9] udpv6: Check address length before reading address family

KMSAN will complain if valid address length passed to udpv6_pre_connect()
is shorter than sizeof("struct sockaddr"->sa_family) bytes.

(This patch is bogus if it is guaranteed that udpv6_pre_connect() is
always called after checking "struct sockaddr"->sa_family. In that case,
we want a comment why we don't need to check valid address length here.)

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 net/ipv6/udp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index d538fafaf4a9..2464fba569b4 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1045,6 +1045,8 @@ static void udp_v6_flush_pending_frames(struct sock *sk)
 static int udpv6_pre_connect(struct sock *sk, struct sockaddr *uaddr,
 			     int addr_len)
 {
+	if (addr_len < offsetofend(struct sockaddr, sa_family))
+		return -EINVAL;
 	/* The following checks are replicated from __ip6_datagram_connect()
 	 * and intended to prevent BPF program called below from accessing
 	 * bytes that are out of the bound specified by user in addr_len.
-- 
2.16.5