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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>
This commit is contained in:
Ross Lagerwall 2019-01-17 15:34:38 +00:00 committed by David S. Miller
parent e40e2a2e78
commit 6c57f04580
5 changed files with 5 additions and 0 deletions
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1
drivers/net/ppp/pppoe.c
View File

@ -445,6 +445,7 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
if (pskb_trim_rcsum(skb, len)) if (pskb_trim_rcsum(skb, len))
goto drop; goto drop;
ph = pppoe_hdr(skb);
pn = pppoe_pernet(dev_net(dev)); pn = pppoe_pernet(dev_net(dev));
/* Note that get_item does a sock_hold(), so sk_pppox(po) /* Note that get_item does a sock_hold(), so sk_pppox(po)

1
include/linux/skbuff.h
View File

@ -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 * This is exactly the same as pskb_trim except that it ensures the
* checksum of received packets are still valid after the operation. * 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) 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); IPSTATS_MIB_INDISCARDS);
goto drop; goto drop;
} }
hdr = ipv6_hdr(skb);
} }
if (hdr->nexthdr == NEXTHDR_HOP && br_nf_check_hbh_len(skb)) if (hdr->nexthdr == NEXTHDR_HOP && br_nf_check_hbh_len(skb))
goto drop; goto drop;

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

@ -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))) pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
return false; return false;
ip6h = ipv6_hdr(skb);
thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo); thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0) if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
return false; return false;

1
net/ipv4/ip_input.c
View File

@ -488,6 +488,7 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
goto drop; goto drop;
} }
iph = ip_hdr(skb);
skb->transport_header = skb->network_header + iph->ihl*4; skb->transport_header = skb->network_header + iph->ihl*4;
/* Remove any debris in the socket control block */ /* Remove any debris in the socket control block */