On Tue, 2 Oct 2012, Linux Kernel Mailing List wrote:
> Gitweb:
> http://git.kernel.org/linus/;a=commit;h=c12b395a46646bab69089ce7016ac78177f6001f
> Commit: c12b395a46646bab69089ce7016ac78177f6001f
> Parent: b7bc2a5b5bd99b216c3e5fe68c7f45c684ab5745
> Author: [email protected] <[email protected]>
> AuthorDate: Fri Aug 10 00:51:50 2012 +0000
> Committer: David S. Miller <[email protected]>
> CommitDate: Tue Aug 14 14:28:32 2012 -0700
>
> gre: Support GRE over IPv6
>
> GRE over IPv6 implementation.
>
> Signed-off-by: Dmitry Kozlov <[email protected]>
> Signed-off-by: David S. Miller <[email protected]>
> --- /dev/null
> +++ b/net/ipv6/ip6_gre.c
> +static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
> + struct net_device *dev,
> + __u8 dsfield,
> + struct flowi6 *fl6,
> + int encap_limit,
> + __u32 *pmtu)
> +{
> + struct net *net = dev_net(dev);
> + struct ip6_tnl *tunnel = netdev_priv(dev);
> + struct net_device *tdev; /* Device to other host */
> + struct ipv6hdr *ipv6h; /* Our new IP header */
> + unsigned int max_headroom; /* The extra header space needed */
max_headroom is not initialized
> + mtu = dst_mtu(dst) - sizeof(*ipv6h);
> + if (encap_limit >= 0) {
> + max_headroom += 8;
Hence gcc (4.1.2) rightfully complains:
net/ipv6/ip6_gre.c: In function ‘ip6gre_xmit2’:
net/ipv6/ip6_gre.c:713: warning: ‘max_headroom’ is used uninitialized in this
function
However, initializing max_headroom to zero at the top, or replacing the line
above by "max_headroom = 8" doesn't seem to be the right fix...
> + mtu -= 8;
> + }
> + if (mtu < IPV6_MIN_MTU)
> + mtu = IPV6_MIN_MTU;
> + if (skb_dst(skb))
> + skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
> + if (skb->len > mtu) {
> + *pmtu = mtu;
> + err = -EMSGSIZE;
> + goto tx_err_dst_release;
> + }
> +
> + if (tunnel->err_count > 0) {
> + if (time_before(jiffies,
> + tunnel->err_time + IP6TUNNEL_ERR_TIMEO)) {
> + tunnel->err_count--;
> +
> + dst_link_failure(skb);
> + } else
> + tunnel->err_count = 0;
> + }
> +
> + max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen + dst->header_len;
... as max_headroom is overwritten here anyway?
So something is really wrong here. What is the right fix?
This issue is present in current mainline as of v3.7.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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