Re: [PATCH -stable 3.10 3.12 3.13] core, nfqueue, openvswitch: fix compilation warning

[Kamal Mostafa <kamal@canonical.com>]

On Mon, 2015-04-13 at 16:41 +0200, Jiri Slaby wrote:
> Stable commit "core, nfqueue, openvswitch: Orphan frags in
> skb_zerocopy and handle errors", upstream commit
> 36d5fe6a000790f56039afe26834265db0a3ad4c, was not correctly backported
> and missed to change a const 'from' parameter to non-const.  This
> results in a new batch of warnings:

Just FYI, the backport in 3.13-stable[0] -- Ben Hutchings' work --
actually does not exhibit this problem.  nfqnl_zcopy() already has the
const removed and the file yields no compile warnings.

Thanks very much for the heads-up anyway, Jiri!

 -Kamal

[0] http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=commitdiff;h=f2287ffc0e9c3d39cbc4ea9e2312640758201dfc


> net/netfilter/nfnetlink_queue_core.c: In function ‘nfqnl_zcopy’:
> net/netfilter/nfnetlink_queue_core.c:272:2: warning: passing argument 1 of ‘skb_orphan_frags’ discards ‘const’ qualifier from pointer target type [enabled by default]
>   if (unlikely(skb_orphan_frags(from, GFP_ATOMIC))) {
>   ^
> In file included from net/netfilter/nfnetlink_queue_core.c:18:0:
> include/linux/skbuff.h:1822:19: note: expected ‘struct sk_buff *’ but argument is of type ‘const struct sk_buff *’
>  static inline int skb_orphan_frags(struct sk_buff *skb, gfp_t gfp_mask)
>                    ^
> net/netfilter/nfnetlink_queue_core.c:273:3: warning: passing argument 1 of ‘skb_tx_error’ discards ‘const’ qualifier from pointer target type [enabled by default]
>    skb_tx_error(from);
>    ^
> In file included from net/netfilter/nfnetlink_queue_core.c:18:0:
> include/linux/skbuff.h:630:13: note: expected ‘struct sk_buff *’ but argument is of type ‘const struct sk_buff *’
>  extern void skb_tx_error(struct sk_buff *skb);
> 
> Remove const from the 'from' parameter, the same as in the upstream
> commit.
> 
> As far as I can see, this leaked into 3.10, 3.12, and 3.13 already.
> 
> Cc: Zoltan Kiss <zoltan.kiss@citrix.com>
> Cc: David S. Miller <davem@davemloft.net>
> Cc: Ben Hutchings <ben@decadent.org.uk>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Kamal Mostafa <kamal.mostafa@canonical.com>
> Cc: stable@vger.kernel.org # v3.10, v3.12, v3.13
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> ---
>  net/netfilter/nfnetlink_queue_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
> index f5c34db24498..8abb522ec322 100644
> --- a/net/netfilter/nfnetlink_queue_core.c
> +++ b/net/netfilter/nfnetlink_queue_core.c
> @@ -236,7 +236,7 @@ nfqnl_flush(struct nfqnl_instance *queue, nfqnl_cmpfn cmpfn, unsigned long data)
>  }
>  
>  static int
> -nfqnl_zcopy(struct sk_buff *to, const struct sk_buff *from, int len, int hlen)
> +nfqnl_zcopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
>  {
>  	int i, j = 0;
>  	int plen = 0; /* length of skb->head fragment */