From 2d5ff7e339d04622d8282661df36151906d0e1c7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 20 Aug 2024 16:08:59 +0000 Subject: ipv6: prevent possible UAF in ip6_xmit() 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 Cc: Vasily Averin Reviewed-by: David Ahern Link: https://patch.msgid.link/20240820160859.3786976-4-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/ipv6/ip6_output.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'net') diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 1b9ebee7308f..f26841f1490f 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -287,11 +287,15 @@ 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) { -- cgit v1.2.3