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Commit 1bf3751e authored by Johannes Berg's avatar Johannes Berg Committed by David S. Miller
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ipv4: ip_check_defrag must not modify skb before unsharing 



ip_check_defrag() might be called from af_packet within the
RX path where shared SKBs are used, so it must not modify
the input SKB before it has unshared it for defragmentation.
Use skb_copy_bits() to get the IP header and only pull in
everything later.

The same is true for the other caller in macvlan as it is
called from dev->rx_handler which can also get a shared SKB.

Reported-by: default avatarEric Leblond <eric@regit.org>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5e1f5420

net/ipv4/ip_fragment.c

+9 −10
Original line number Diff line number Diff line
@@ -707,28 +707,27 @@ EXPORT_SYMBOL(ip_defrag); 


struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)

{

	const struct iphdr *iph;

	struct iphdr iph;

	u32 len;



	if (skb->protocol != htons(ETH_P_IP))

		return skb;



	if (!pskb_may_pull(skb, sizeof(struct iphdr)))

	if (!skb_copy_bits(skb, 0, &iph, sizeof(iph)))

		return skb;



	iph = ip_hdr(skb);

	if (iph->ihl < 5 || iph->version != 4)

		return skb;

	if (!pskb_may_pull(skb, iph->ihl*4))

	if (iph.ihl < 5 || iph.version != 4)

		return skb;

	iph = ip_hdr(skb);

	len = ntohs(iph->tot_len);

	if (skb->len < len || len < (iph->ihl * 4))



	len = ntohs(iph.tot_len);

	if (skb->len < len || len < (iph.ihl * 4))

		return skb;



	if (ip_is_fragment(ip_hdr(skb))) {

	if (ip_is_fragment(&iph)) {

		skb = skb_share_check(skb, GFP_ATOMIC);

		if (skb) {

			if (!pskb_may_pull(skb, iph.ihl*4))

				return skb;

			if (pskb_trim_rcsum(skb, len))

				return skb;

			memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));