linux-kernel - [PATCH net-next v2 3/6] ipmr: fix incorrect parameter validation in the ip_mroute

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Date: Thu, 7 Mar 2024 14:23:50 +0000
From: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
To: "David S. Miller" <davem@...emloft.net>
CC: David Ahern <dsahern@...nel.org>, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Simon
 Horman" <horms@...nel.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "lvc-project@...uxtesting.org"
	<lvc-project@...uxtesting.org>
Subject: [PATCH net-next v2 3/6] ipmr: fix incorrect parameter validation in
 the ip_mroute_getsockopt() function

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@...otecs.ru>
---
V2:
 - reword the patch description
 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 362229836510..b53c36c473a5 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1603,9 +1603,11 @@ 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))
-- 
2.39.2