From: Johannes Berg <johannes.berg@xxxxxxxxx>
ip_check_defrag() might be called from af_packet within the
RX path where shared SKBs are used, so it must not modify
the input SKB before it has unshared it for defragmentation.
Use skb_copy_bits() to get the IP header and only pull in
everything later.
The same is true for the other caller in macvlan as it is
called from dev->rx_handler which can also get a shared SKB.
Reported-by: Eric Leblond <eric@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
For some versions of the kernel, this code goes into af_packet.c
net/ipv4/ip_fragment.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 448e685..8d5cc75 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -707,28 +707,27 @@ EXPORT_SYMBOL(ip_defrag);
struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
{
- const struct iphdr *iph;
+ struct iphdr iph;
u32 len;
if (skb->protocol != htons(ETH_P_IP))
return skb;
- if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+ if (!skb_copy_bits(skb, 0, &iph, sizeof(iph)))
return skb;
- iph = ip_hdr(skb);
- if (iph->ihl < 5 || iph->version != 4)
+ if (iph.ihl < 5 || iph.version != 4)
return skb;
- if (!pskb_may_pull(skb, iph->ihl*4))
- return skb;
- iph = ip_hdr(skb);
- len = ntohs(iph->tot_len);
- if (skb->len < len || len < (iph->ihl * 4))
+
+ len = ntohs(iph.tot_len);
+ if (skb->len < len || len < (iph.ihl * 4))
return skb;
- if (ip_is_fragment(ip_hdr(skb))) {
+ if (ip_is_fragment(&iph)) {
skb = skb_share_check(skb, GFP_ATOMIC);
if (skb) {
+ if (!pskb_may_pull(skb, iph.ihl*4))
+ return skb;
if (pskb_trim_rcsum(skb, len))
return skb;
memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
--
1.8.0
--
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