Commit e94e50bd authored Dec 21, 2018 by Paolo Abeni Committed by David S. Miller Dec 21, 2018

net: fix possible user-after-free in skb_ext_add()



On cow we can free the old extension: we must avoid dereferencing
such extension after skb_ext_maybe_cow(). Since 'new' contents
are always equal to 'old' after the copy, we can fix the above
accessing the relevant data using 'new'.

Fixes: df5042f4 ("sk_buff: add skb extension infrastructure")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7fa4bd73

net/core/skbuff.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -5666,13 +5666,13 @@ void skb_ext_add(struct sk_buff skb, enum skb_ext_id id)
		if (!new)
		return NULL;

		if (__skb_ext_exist(old, id)) {
		if (__skb_ext_exist(new, id)) {
		if (old != new)
		skb->extensions = new;
		goto set_active;
		}

		newoff = old->chunks;
		newoff = new->chunks;
		} else {
		newoff = SKB_EXT_CHUNKSIZEOF(*new);

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