6.12-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 628e6d18930bbd21f2d4562228afe27694f66da9 ]
ndisc_alloc_skb() can be called without RTNL or RCU being held.
Add RCU protection to avoid possible UAF.
Fixes: de09334b9326 ("ndisc: Introduce ndisc_alloc_skb() helper.") 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/20250207135841.1948589-3-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/ndisc.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 264b10a947577..90f8aa2d7af2e 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -418,15 +418,11 @@ static struct sk_buff *ndisc_alloc_skb(struct net_device *dev, { int hlen = LL_RESERVED_SPACE(dev); int tlen = dev->needed_tailroom; - struct sock *sk = dev_net(dev)->ipv6.ndisc_sk; struct sk_buff *skb;
skb = alloc_skb(hlen + sizeof(struct ipv6hdr) + len + tlen, GFP_ATOMIC); - if (!skb) { - ND_PRINTK(0, err, "ndisc: %s failed to allocate an skb\n", - __func__); + if (!skb) return NULL; - }
skb->protocol = htons(ETH_P_IPV6); skb->dev = dev; @@ -437,7 +433,9 @@ static struct sk_buff *ndisc_alloc_skb(struct net_device *dev, /* Manually assign socket ownership as we avoid calling * sock_alloc_send_pskb() to bypass wmem buffer limits */ - skb_set_owner_w(skb, sk); + rcu_read_lock(); + skb_set_owner_w(skb, dev_net_rcu(dev)->ipv6.ndisc_sk); + rcu_read_unlock();
return skb; }