[PATCH 5.15 148/317] ipmr: fix incorrect parameter validation in the ip_mroute_getsockopt() function

[Sasha Levin]

From: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>

[ Upstream commit 5c3be3e0eb44b7f978bb6cbb20ad956adb93f736 ]

The 'olr' 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 'olr' as read from 'optlen',
where the types of relevant variables are (signed) int.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ipv4/ipmr.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index eb3c09340aef8..c9a633559258c 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1574,9 +1574,11 @@ int ip_mroute_getsockopt(struct sock *sk, int optname, sockptr_t optval,
 
 	if (copy_from_sockptr(&olr, optlen, sizeof(int)))
 		return -EFAULT;
-	olr = min_t(unsigned int, olr, sizeof(int));
 	if (olr < 0)
 		return -EINVAL;
+
+	olr = min_t(unsigned int, olr, sizeof(int));
+
 	if (copy_to_sockptr(optlen, &olr, sizeof(int)))
 		return -EFAULT;
 	if (copy_to_sockptr(optval, &val, olr))
-- 
2.43.0