netdev - [PATCH AUTOSEL 5.1 30/95] bpf: udp: ipv6: Avoid running reuseport's bpf_prog from __udp6_lib

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Date:   Wed, 26 Jun 2019 20:29:15 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Martin KaFai Lau <kafai@...com>, Craig Gallek <kraig@...gle.com>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 5.1 30/95] bpf: udp: ipv6: Avoid running reuseport's bpf_prog from __udp6_lib_err

From: Martin KaFai Lau <kafai@...com>

[ Upstream commit 4ac30c4b3659efac031818c418beb51e630d512d ]

__udp6_lib_err() may be called when handling icmpv6 message. For example,
the icmpv6 toobig(type=2).  __udp6_lib_lookup() is then called
which may call reuseport_select_sock().  reuseport_select_sock() will
call into a bpf_prog (if there is one).

reuseport_select_sock() is expecting the skb->data pointing to the
transport header (udphdr in this case).  For example, run_bpf_filter()
is pulling the transport header.

However, in the __udp6_lib_err() path, the skb->data is pointing to the
ipv6hdr instead of the udphdr.

One option is to pull and push the ipv6hdr in __udp6_lib_err().
Instead of doing this, this patch follows how the original
commit 538950a1b752 ("soreuseport: setsockopt SO_ATTACH_REUSEPORT_[CE]BPF")
was done in IPv4, which has passed a NULL skb pointer to
reuseport_select_sock().

Fixes: 538950a1b752 ("soreuseport: setsockopt SO_ATTACH_REUSEPORT_[CE]BPF")
Cc: Craig Gallek <kraig@...gle.com>
Signed-off-by: Martin KaFai Lau <kafai@...com>
Acked-by: Song Liu <songliubraving@...com>
Acked-by: Craig Gallek <kraig@...gle.com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/ipv6/udp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 622eeaf5732b..767583c12bf2 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -516,7 +516,7 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	struct net *net = dev_net(skb->dev);

 	sk = __udp6_lib_lookup(net, daddr, uh->dest, saddr, uh->source,
-			       inet6_iif(skb), inet6_sdif(skb), udptable, skb);
+			       inet6_iif(skb), inet6_sdif(skb), udptable, NULL);
 	if (!sk) {
 		/* No socket for error: try tunnels before discarding */
 		sk = ERR_PTR(-ENOENT);
-- 
2.20.1