forked from Minki/linux
ip6_gre: fix ip6gre_err() invalid reads
Andrey Konovalov reported out of bound accesses in ip6gre_err()
If GRE flags contains GRE_KEY, the following expression
*(((__be32 *)p) + (grehlen / 4) - 1)
accesses data ~40 bytes after the expected point, since
grehlen includes the size of IPv6 headers.
Let's use a "struct gre_base_hdr *greh" pointer to make this
code more readable.
p[1] becomes greh->protocol.
grhlen is the GRE header length.
Fixes: c12b395a46
("gre: Support GRE over IPv6")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
d71b789688
commit
7892032cfe
@ -369,33 +369,35 @@ static void ip6gre_tunnel_uninit(struct net_device *dev)
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static void ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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u8 type, u8 code, int offset, __be32 info)
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{
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const struct ipv6hdr *ipv6h = (const struct ipv6hdr *)skb->data;
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__be16 *p = (__be16 *)(skb->data + offset);
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int grehlen = offset + 4;
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const struct gre_base_hdr *greh;
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const struct ipv6hdr *ipv6h;
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int grehlen = sizeof(*greh);
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struct ip6_tnl *t;
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int key_off = 0;
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__be16 flags;
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__be32 key;
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flags = p[0];
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if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
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if (!pskb_may_pull(skb, offset + grehlen))
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return;
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greh = (const struct gre_base_hdr *)(skb->data + offset);
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flags = greh->flags;
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if (flags & (GRE_VERSION | GRE_ROUTING))
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return;
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if (flags&GRE_KEY) {
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grehlen += 4;
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if (flags & GRE_CSUM)
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grehlen += 4;
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}
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if (flags & GRE_KEY) {
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key_off = grehlen + offset;
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grehlen += 4;
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}
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/* If only 8 bytes returned, keyed message will be dropped here */
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if (!pskb_may_pull(skb, grehlen))
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if (!pskb_may_pull(skb, offset + grehlen))
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return;
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ipv6h = (const struct ipv6hdr *)skb->data;
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p = (__be16 *)(skb->data + offset);
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greh = (const struct gre_base_hdr *)(skb->data + offset);
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key = key_off ? *(__be32 *)(skb->data + key_off) : 0;
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t = ip6gre_tunnel_lookup(skb->dev, &ipv6h->daddr, &ipv6h->saddr,
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flags & GRE_KEY ?
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*(((__be32 *)p) + (grehlen / 4) - 1) : 0,
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p[1]);
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key, greh->protocol);
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if (!t)
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return;
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