Commit f638a84a authored by Wang Yufen's avatar Wang Yufen Committed by Jakub Kicinski
Browse files

ipv6: Fix signed integer overflow in l2tp_ip6_sendmsg 



When len >= INT_MAX - transhdrlen, ulen = len + transhdrlen will be
overflow. To fix, we can follow what udpv6 does and subtract the
transhdrlen from the max.

Signed-off-by: default avatarWang Yufen <wangyufen@huawei.com>
Link: https://lore.kernel.org/r/20220607120028.845916-2-wangyufen@huawei.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent f93431c8

net/l2tp/l2tp_ip6.c

+3 −2
Original line number Diff line number Diff line
@@ -504,14 +504,15 @@ static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 
	struct ipcm6_cookie ipc6;

	int addr_len = msg->msg_namelen;

	int transhdrlen = 4; /* zero session-id */

	int ulen = len + transhdrlen;

	int ulen;

	int err;



	/* Rough check on arithmetic overflow,

	 * better check is made in ip6_append_data().

	 */

	if (len > INT_MAX)

	if (len > INT_MAX - transhdrlen)

		return -EMSGSIZE;

	ulen = len + transhdrlen;



	/* Mirror BSD error message compatibility */

	if (msg->msg_flags & MSG_OOB)