linux-kernel - [PATCH net] net: socket: add check for negative optlen in compat setsockopt

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Message-Id: <20190220213454.244600-1-jannh@google.com>
Date:   Wed, 20 Feb 2019 22:34:54 +0100
From:   Jann Horn <jannh@...gle.com>
To:     "David S. Miller" <davem@...emloft.net>, jannh@...gle.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net] net: socket: add check for negative optlen in compat setsockopt

__sys_setsockopt() already checks for `optlen < 0`. Add an equivalent check
to the compat path for robustness. This has to be `> INT_MAX` instead of
`< 0` because the signedness of `optlen` is different here.

Signed-off-by: Jann Horn <jannh@...gle.com>
---
 net/compat.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/compat.c b/net/compat.c
index 959d1c51826d..3d348198004f 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -388,8 +388,12 @@ static int __compat_sys_setsockopt(int fd, int level, int optname,
 				   char __user *optval, unsigned int optlen)
 {
 	int err;
-	struct socket *sock = sockfd_lookup(fd, &err);
+	struct socket *sock;
+
+	if (optlen > INT_MAX)
+		return -EINVAL;

+	sock = sockfd_lookup(fd, &err);
 	if (sock) {
 		err = security_socket_setsockopt(sock, level, optname);
 		if (err) {
-- 
2.21.0.rc0.258.g878e2cd30e-goog