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 083376ea237e8d3058851cc2a51691fbf1980d3f..41d892bf12cc6a4d45a4dc0c23b447ff2809c518 100644 (file)
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1152,10 +1152,11 @@ 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;