From: Wang Yufen wangyufen@huawei.com
[ 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 --- net/l2tp/l2tp_ip6.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c index 0fa694bd3f6a..23e9ce985ed6 100644 --- a/net/l2tp/l2tp_ip6.c +++ b/net/l2tp/l2tp_ip6.c @@ -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)