neighbour: use RCU protection in __neigh_notify()
[ Upstream commit becbd5850c03ed33b232083dd66c6e38c0c0e569 ]
__neigh_notify() can be called without RTNL or RCU protection.
Use RCU protection to avoid potential UAF.
BUG=b/405560945
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2025-21763 in the Linux kernel.
cos-patch: security-high
Fixes: 426b5303eb43 ("[NETNS]: Modify the neighbour table code so it handles multiple network namespaces")
Change-Id: I8fee291e3781d5b619f01d2d8def4b4636872907
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250207135841.1948589-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/97640
Reviewed-by: Kevin Berry <kpberry@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index b127533..2e2c009 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -3498,10 +3498,12 @@ static const struct seq_operations neigh_stat_seq_ops = {
static void __neigh_notify(struct neighbour *n, int type, int flags,
u32 pid)
{
- struct net *net = dev_net(n->dev);
struct sk_buff *skb;
int err = -ENOBUFS;
+ struct net *net;
+ rcu_read_lock();
+ net = dev_net_rcu(n->dev);
skb = nlmsg_new(neigh_nlmsg_size(), GFP_ATOMIC);
if (skb == NULL)
goto errout;
@@ -3514,9 +3516,11 @@ static void __neigh_notify(struct neighbour *n, int type, int flags,
goto errout;
}
rtnl_notify(skb, net, 0, RTNLGRP_NEIGH, NULL, GFP_ATOMIC);
- return;
+ goto out;
errout:
rtnl_set_sk_err(net, RTNLGRP_NEIGH, err);
+out:
+ rcu_read_unlock();
}
void neigh_app_ns(struct neighbour *n)
