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 39b3c7fbf9f660a72ce185e5e748c47040864c11..7420b4f19b45efe63e32ec2a6366f8321eda3725 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;