[PPP] generic: Call skb_cow_head before scribbling over skb (7b797d5b) · Commits · 戴 / test

It's rude to write over data that other people are still using. So call skb_cow_head before PPP proceeds to modify the skb data. Signed-off-by:

drivers/net/ppp_generic.c

+3 −11

Original line number	Diff line number	Diff line
		@@ -899,17 +899,9 @@ ppp_start_xmit(struct sk_buff skb, struct net_device dev)

		/* Put the 2-byte PPP protocol number on the front,
		making sure there is room for the address and control fields. */
		if (skb_headroom(skb) < PPP_HDRLEN) {
		struct sk_buff *ns;

		ns = alloc_skb(skb->len + dev->hard_header_len, GFP_ATOMIC);
		if (ns == 0)
		if (skb_cow_head(skb, PPP_HDRLEN))
		goto outf;
		skb_reserve(ns, dev->hard_header_len);
		skb_copy_bits(skb, 0, skb_put(ns, skb->len), skb->len);
		kfree_skb(skb);
		skb = ns;
		}

		pp = skb_push(skb, 2);
		proto = npindex_to_proto[npi];
		pp[0] = proto >> 8;