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net: Fix usage of pskb_trim_rcsum

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[ Upstream commit 6c57f0458022298e4da1729c67bd33ce41c14e7a ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ross Lagerwall 2019-01-17 15:34:38 +00:00 • committed by Greg Kroah-Hartman
parent 626b008972
commit 52a30a6e14
5 changed files with 5 additions and 0 deletions
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1
drivers/net/ppp/pppoe.c
View file

@ -442,6 +442,7 @@ 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)

1
include/linux/skbuff.h
View file

@ -2798,6 +2798,7 @@ static inline unsigned char *skb_push_rcsum(struct sk_buff *skb,
*
* 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)

1
net/bridge/br_netfilter_ipv6.c
View file

@ -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;

1
net/bridge/netfilter/nft_reject_bridge.c
View file

@ -192,6 +192,7 @@ 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;

1
net/ipv4/ip_input.c
View file

@ -444,6 +444,7 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
goto drop;
}
iph = ip_hdr(skb);
skb->transport_header = skb->network_header + iph->ihl*4;
/* Remove any debris in the socket control block */