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: Ross Lagerwall <ross.lagerwall@citrix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -445,6 +445,7 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
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if (pskb_trim_rcsum(skb, len))
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goto drop;
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ph = pppoe_hdr(skb);
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pn = pppoe_pernet(dev_net(dev));
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/* Note that get_item does a sock_hold(), so sk_pppox(po)
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@ -3218,6 +3218,7 @@ int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len);
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*
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* This is exactly the same as pskb_trim except that it ensures the
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* checksum of received packets are still valid after the operation.
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* It can change skb pointers.
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*/
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static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
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@ -131,6 +131,7 @@ int br_validate_ipv6(struct net *net, struct sk_buff *skb)
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IPSTATS_MIB_INDISCARDS);
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goto drop;
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}
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hdr = ipv6_hdr(skb);
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}
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if (hdr->nexthdr == NEXTHDR_HOP && br_nf_check_hbh_len(skb))
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goto drop;
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@ -229,6 +229,7 @@ static bool reject6_br_csum_ok(struct sk_buff *skb, int hook)
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pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
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return false;
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ip6h = ipv6_hdr(skb);
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thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
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if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
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return false;
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@ -488,6 +488,7 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
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goto drop;
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}
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iph = ip_hdr(skb);
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skb->transport_header = skb->network_header + iph->ihl*4;
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/* Remove any debris in the socket control block */
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