net: kcm: fix incorrect parameter validation in the kcm_getsockopt) function

[ Upstream commit 3ed5f415133f9b7518fbe55ba9ae9a3f5e700929 ]

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

To fix the logic, check 'len' as read from 'optlen',
where the types of relevant variables are (signed) int.

Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 0d1ab4149553c6ba422152a134a9b723fd8170ca..5457ca1909801bd298b89d13443ed67dbed1e319 100644 (file)
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1275,10 +1275,11 @@ static int kcm_getsockopt(struct socket *sock, int level, int optname,
        if (get_user(len, optlen))
                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 KCM_RECV_DISABLE:
                val = kcm->rx_disabled;