netdev - [PATCH net 3/3] ipv6: prevent possible UAF in ip6

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240819134827.2989452-4-edumazet@google.com>
Date: Mon, 19 Aug 2024 13:48:27 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, Vasily Averin <vvs@...tuozzo.com>
Subject: [PATCH net 3/3] 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 <edumazet@...gle.com>
Cc: Vasily Averin <vvs@...tuozzo.com>
---
 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 1b9ebee7308f02a626c766de1794e6b114ae8554..519690514b2d1520a311adbcfaa8c6a69b1e85d3 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) {
+			rcu_read_unlock();
 			IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
 			return -ENOBUFS;
 		}
+		rcu_read_unlock();
 	}
 
 	if (opt) {
-- 
2.46.0.184.g6999bdac58-goog