linux-kernel - [PATCH net-next] tcp: fix incorrect parameter validation in the do_tcp

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Date: Wed, 6 Mar 2024 09:57:50 +0000
From: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
To: Eric Dumazet <edumazet@...gle.com>
CC: "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>
Subject: [PATCH net-next] tcp: fix incorrect parameter validation in the
 do_tcp_getsockopt() function

The 'len' variable can't be negative because all 'min_t' parameters
cast to unsigned int, and then the minimum one is chosen.

To fix it, move the if statement higher.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
---
 net/ipv4/tcp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c82dc42f57c6..a4f418592314 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4010,11 +4010,11 @@ int do_tcp_getsockopt(struct sock *sk, int level,
 	if (copy_from_sockptr(&len, optlen, sizeof(int)))
 		return -EFAULT;
 
-	len = min_t(unsigned int, len, sizeof(int));
-
 	if (len < 0)
 		return -EINVAL;
 
+	len = min_t(unsigned int, len, sizeof(int));
+
 	switch (optname) {
 	case TCP_MAXSEG:
 		val = tp->mss_cache;
-- 
2.39.2