Commit 2f42389d authored Jun 07, 2022 by Wang Yufen Committed by Greg Kroah-Hartman Jun 22, 2022

ipv6: Fix signed integer overflow in l2tp_ip6_sendmsg



[ Upstream commit f638a84afef3dfe10554c51820c16e39a278c915 ]

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: Wang Yufen <wangyufen@huawei.com>
Link: https://lore.kernel.org/r/20220607120028.845916-2-wangyufen@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 6b4d8b44

net/l2tp/l2tp_ip6.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -515,14 +515,15 @@ 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)