5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 2d5ff7e339d04622d8282661df36151906d0e1c7 ]
If skb_expand_head() returns NULL, skb has been freed
and the associated dst/idev could also have been freed.
We must use rcu_read_lock() to prevent a possible UAF.
Fixes: 0c9f227bee11 ("ipv6: use skb_expand_head in ip6_xmit")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Vasily Averin <vasily.averin@xxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Link: https://patch.msgid.link/20240820160859.3786976-4-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/ipv6/ip6_output.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 8054a4a2f2a5e..b37121f872bc9 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -273,11 +273,15 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
head_room += opt->opt_nflen + opt->opt_flen;
if (unlikely(head_room > skb_headroom(skb))) {
+ /* Make sure idev stays alive */
+ rcu_read_lock();
skb = skb_expand_head(skb, head_room);
if (!skb) {
IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
+ rcu_read_unlock();
return -ENOBUFS;
}
+ rcu_read_unlock();
}
if (opt) {
--
2.43.0
