Hello,
On Mon, 2012-12-10 at 10:41 +0100, Johannes Berg wrote:
> 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.
I've applied the patch and built a new kernel. I did not manage to get
it crashed when using the two techniques (suspend to ram and down/up
interface) that were working well to crash kernel without the patch.
BR,
> 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));
--
Eric Leblond <eric@xxxxxxxxx>
Blog: https://home.regit.org/
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