Subject: [PATCH net-next] ipv4: potential underflow in compat_ip_setsockopt()

From: Dan Carpenter <[email-masked]>
Date: Sat, 23 May 2020 20:46:48 +0300

The value of "n" is capped at 0x1ffffff but it checked for negative
values.  I don't think this causes a problem but I'm not certain and
it's harmless to prevent it.

Fixes: 2e04172875c9 ("ipv4: do compat setsockopt for MCAST_MSFILTER directly")
Signed-off-by: Dan Carpenter <[email-masked]>
---

 net/ipv4/ip_sockglue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index a2469bc57cfe..f43d5f12aa86 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1347,8 +1347,8 @@ int compat_ip_setsockopt(struct sock *sk, int level, int optname,
 	{
 		const int size0 = offsetof(struct compat_group_filter, gf_slist);
 		struct compat_group_filter *gf32;
+		unsigned int n;
 		void *p;
-		int n;
 
 		if (optlen < size0)
 			return -EINVAL;
-- 
2.26.2