On Tue, 2014-03-18 at 15:24 +0100, Bjørn Mork wrote:

Ben Hutchings [off-list ref] writes:

quoted

On Mon, 2014-03-17 at 23:27 -0700, Eric W. Biederman wrote:
[...]

quoted

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c

@@ -554,14 +554,21 @@ static void kfree_skbmem(struct sk_buff *skb)
 
 static void skb_release_head_state(struct sk_buff *skb)
 {
+	WARN_ONCE(in_irq() && !skb_irq_freeable(skb),
+		  "%s called from irq! sp %d nfct %d frag_list %d %pF dst %lx",
+		  __func__,
+		  IS_ENABLED(CONFIG_XFRM) ? !!skb->sp : 0,
+		  IS_ENABLED(CONFIG_NF_CONNTRACK) ? !!skb->nfct : 0,

[...]

This is a syntax error if CONFIG_XFRM or CONFIG_NF_CONNTRACK is
disabled; you have to use #ifdef's.

Are you sure?  I thought one of the ideas behind these macros was that
they would always evaluate to 0 or 1.  The docs says:

 * IS_ENABLED(CONFIG_FOO) evaluates to 1 if CONFIG_FOO is set to 'y' or 'm',
 * 0 otherwise.


See include/linux/kconfig.h for the macro magic making this
happen. Looks like fun figuring that out.

It has nothing to do with this.

Try following code, and you'll get a compilation error.

unsigned int can_this_fly(struct sk_buff *skb)
{
	return IS_ENABLED(CONFIG_NOWAY_SIR) ? skb->unknown_field : 0;
}