[PATCH 4.14 12/37] igmp: Fix a data-race around sysctl_igmp_max_memberships.

Greg Kroah-Hartman
2022-07-27T16:28:00Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 6305d821e3b9b5379d348528e5b5faf316383bc2 ]

While reading sysctl_igmp_max_memberships, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/igmp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 4b3875acc876..fd2c634eeee4 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -2179,7 +2179,7 @@ int ip_mc_join_group(struct sock *sk, struct ip_mreqn *imr)
count++;
}
err = -ENOBUFS;
- if (count >= net->ipv4.sysctl_igmp_max_memberships)
+ if (count >= READ_ONCE(net->ipv4.sysctl_igmp_max_memberships))
goto done;
iml = sock_kmalloc(sk, sizeof(*iml), GFP_KERNEL);
if (!iml)
--
2.35.1