On Fri, Dec 13, 2013 at 01:01:59PM +0000, Mark Hambleton wrote:
> Hi,
>
> Following a recent commit to LTS and upstream I see the following warning emitted on an ARM32 build:
>
> net/ipv6/udp_offload.c: In function 'udp6_ufo_fragment':
> net/ipv6/udp_offload.c:88:22: error: comparison between pointer and integer [-Werror]
> if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
> ^
> cc1: all warnings being treated as errors
> make[2]: *** [net/ipv6/udp_offload.o] Error 1
> make[1]: *** [net/ipv6] Error 2
>
> The commit made the following changes:
>
> - if (skb_headroom(skb) < (tnl_hlen + frag_hdr_sz)) {
> + if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
>
> Now, because of some defines in skbuff.h :
>
> #if BITS_PER_LONG > 32
> #define NET_SKBUFF_DATA_USES_OFFSET 1
> #endif
>
> #ifdef NET_SKBUFF_DATA_USES_OFFSET
> typedef unsigned int sk_buff_data_t;
> #else
> typedef unsigned char *sk_buff_data_t;
> #endif
>
> On an ARM32 system sk_buff_data_t would be a pointer (long being 32 bits), meaning that skb->mac_header is a pointer and that you are comparing a pointer against a length, which doesn't look like it is correct to me?
>
> I can see how this works when NET_SKBUFF_DATA_USES_OFFSET is defined, but is there a way to do this that works for both cases?
Sorry, I don't know which version the LTS kernel is. Upstream does not use
sk_buff_data_t for mac_header any more.
Something like that might help:
(skb_mac_header(skb) < skb->head + tnl_hlen + frag_hdr_sz)
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