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Commit 6c57f045 authored by Ross Lagerwall's avatar Ross Lagerwall Committed by David S. Miller
Browse files

net: Fix usage of pskb_trim_rcsum 



In certain cases, pskb_trim_rcsum() may change skb pointers.
Reinitialize header pointers afterwards to avoid potential
use-after-frees. Add a note in the documentation of
pskb_trim_rcsum(). Found by KASAN.

Signed-off-by: default avatarRoss Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e40e2a2e

drivers/net/ppp/pppoe.c

+1 −0
Original line number Diff line number Diff line
@@ -445,6 +445,7 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev, 
	if (pskb_trim_rcsum(skb, len))

		goto drop;



	ph = pppoe_hdr(skb);

	pn = pppoe_pernet(dev_net(dev));



	/* Note that get_item does a sock_hold(), so sk_pppox(po)

include/linux/skbuff.h

+1 −0
Original line number Diff line number Diff line
@@ -3218,6 +3218,7 @@ int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len); 
 *

 *	This is exactly the same as pskb_trim except that it ensures the

 *	checksum of received packets are still valid after the operation.

 *	It can change skb pointers.

 */



static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)

net/bridge/br_netfilter_ipv6.c

+1 −0
Original line number Diff line number Diff line
@@ -131,6 +131,7 @@ int br_validate_ipv6(struct net *net, struct sk_buff *skb) 
					IPSTATS_MIB_INDISCARDS);

			goto drop;

		}

		hdr = ipv6_hdr(skb);

	}

	if (hdr->nexthdr == NEXTHDR_HOP && br_nf_check_hbh_len(skb))

		goto drop;

net/bridge/netfilter/nft_reject_bridge.c

+1 −0
Original line number Diff line number Diff line
@@ -229,6 +229,7 @@ static bool reject6_br_csum_ok(struct sk_buff *skb, int hook) 
	    pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))

		return false;



	ip6h = ipv6_hdr(skb);

	thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);

	if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)

		return false;

net/ipv4/ip_input.c

+1 −0
Original line number Diff line number Diff line
@@ -488,6 +488,7 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net) 
		goto drop;

	}



	iph = ip_hdr(skb);

	skb->transport_header = skb->network_header + iph->ihl*4;



	/* Remove any debris in the socket control block */