Subject: Re: [Bisected] [1b4fa28a8b07] Build failure "net/core/gso_test.c"

From: Kees Cook <[email-masked]>
Date: Thu, 12 Oct 2023 09:29:11 -0700

On Thu, Oct 12, 2023 at 11:57:46AM +0200, Florian Westphal wrote:
> Tasmiya Nalatwad <[email-masked]> wrote:
> > Greetings,
> > 
> > [net-next] [6.6-rc4] Build failure "net/core/gso_test.c"
> > 
> > --- Traces ---
> > 
> > make -j 33 -s && make modules_install && make install
> > net/core/gso_test.c:58:48: error: initializer element is not constant
> >    58 |                 .segs = (const unsigned int[]) { gso_size },
> >       |                                                ^
> 
> Ouch, I can reproduce this with: gcc --version
> gcc (Debian 12.2.0-14) 12.2.0
> Copyright (C) 2022 Free Software Foundation, Inc.
> 
> gcc 13.2.1 and clang-16.0.6 are ok.
> 
> Whats the preference here?  We could use simple preprocessor constant
> or we could require much more recent compiler version for the net
> kunit tests via kconfig.
> 
> gcc-12.2.0 can compile it after this simple s//g "fix":
> 
> diff --git a/net/core/gso_test.c b/net/core/gso_test.c
> --- a/net/core/gso_test.c
> +++ b/net/core/gso_test.c
> @@ -4,7 +4,7 @@
>  #include <linux/skbuff.h>
>  
>  static const char hdr[] = "abcdefgh";
> -static const int gso_size = 1000;
> +#define GSO_TEST_SIZE 1000

This fixes the build for me too.

Tested-by: Kees Cook <[email-masked]>
Reviewed-by: Kees Cook <[email-masked]>

-Kees

>  
>  static void __init_skb(struct sk_buff *skb)
>  {
> @@ -18,7 +18,7 @@ static void __init_skb(struct sk_buff *skb)
>  
>  	/* proto is arbitrary, as long as not ETH_P_TEB or vlan */
>  	skb->protocol = htons(ETH_P_ATALK);
> -	skb_shinfo(skb)->gso_size = gso_size;
> +	skb_shinfo(skb)->gso_size = GSO_TEST_SIZE;
>  }
>  
>  enum gso_test_nr {
> @@ -53,70 +53,70 @@ static struct gso_test_case cases[] = {
>  	{
>  		.id = GSO_TEST_NO_GSO,
>  		.name = "no_gso",
> -		.linear_len = gso_size,
> +		.linear_len = GSO_TEST_SIZE,
>  		.nr_segs = 1,
> -		.segs = (const unsigned int[]) { gso_size },
> +		.segs = (const unsigned int[]) { GSO_TEST_SIZE },
>  	},
>  	{
>  		.id = GSO_TEST_LINEAR,
>  		.name = "linear",
> -		.linear_len = gso_size + gso_size + 1,
> +		.linear_len = GSO_TEST_SIZE + GSO_TEST_SIZE + 1,
>  		.nr_segs = 3,
> -		.segs = (const unsigned int[]) { gso_size, gso_size, 1 },
> +		.segs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE, 1 },
>  	},
>  	{
>  		.id = GSO_TEST_FRAGS,
>  		.name = "frags",
> -		.linear_len = gso_size,
> +		.linear_len = GSO_TEST_SIZE,
>  		.nr_frags = 2,
> -		.frags = (const unsigned int[]) { gso_size, 1 },
> +		.frags = (const unsigned int[]) { GSO_TEST_SIZE, 1 },
>  		.nr_segs = 3,
> -		.segs = (const unsigned int[]) { gso_size, gso_size, 1 },
> +		.segs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE, 1 },
>  	},
>  	{
>  		.id = GSO_TEST_FRAGS_PURE,
>  		.name = "frags_pure",
>  		.nr_frags = 3,
> -		.frags = (const unsigned int[]) { gso_size, gso_size, 2 },
> +		.frags = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE, 2 },
>  		.nr_segs = 3,
> -		.segs = (const unsigned int[]) { gso_size, gso_size, 2 },
> +		.segs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE, 2 },
>  	},
>  	{
>  		.id = GSO_TEST_GSO_PARTIAL,
>  		.name = "gso_partial",
> -		.linear_len = gso_size,
> +		.linear_len = GSO_TEST_SIZE,
>  		.nr_frags = 2,
> -		.frags = (const unsigned int[]) { gso_size, 3 },
> +		.frags = (const unsigned int[]) { GSO_TEST_SIZE, 3 },
>  		.nr_segs = 2,
> -		.segs = (const unsigned int[]) { 2 * gso_size, 3 },
> +		.segs = (const unsigned int[]) { 2 * GSO_TEST_SIZE, 3 },
>  	},
>  	{
>  		/* commit 89319d3801d1: frag_list on mss boundaries */
>  		.id = GSO_TEST_FRAG_LIST,
>  		.name = "frag_list",
> -		.linear_len = gso_size,
> +		.linear_len = GSO_TEST_SIZE,
>  		.nr_frag_skbs = 2,
> -		.frag_skbs = (const unsigned int[]) { gso_size, gso_size },
> +		.frag_skbs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE },
>  		.nr_segs = 3,
> -		.segs = (const unsigned int[]) { gso_size, gso_size, gso_size },
> +		.segs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE, GSO_TEST_SIZE },
>  	},
>  	{
>  		.id = GSO_TEST_FRAG_LIST_PURE,
>  		.name = "frag_list_pure",
>  		.nr_frag_skbs = 2,
> -		.frag_skbs = (const unsigned int[]) { gso_size, gso_size },
> +		.frag_skbs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE },
>  		.nr_segs = 2,
> -		.segs = (const unsigned int[]) { gso_size, gso_size },
> +		.segs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE },
>  	},
>  	{
>  		/* commit 43170c4e0ba7: GRO of frag_list trains */
>  		.id = GSO_TEST_FRAG_LIST_NON_UNIFORM,
>  		.name = "frag_list_non_uniform",
> -		.linear_len = gso_size,
> +		.linear_len = GSO_TEST_SIZE,
>  		.nr_frag_skbs = 4,
> -		.frag_skbs = (const unsigned int[]) { gso_size, 1, gso_size, 2 },
> +		.frag_skbs = (const unsigned int[]) { GSO_TEST_SIZE, 1, GSO_TEST_SIZE, 2 },
>  		.nr_segs = 4,
> -		.segs = (const unsigned int[]) { gso_size, gso_size, gso_size, 3 },
> +		.segs = (const unsigned int[]) { GSO_TEST_SIZE, GSO_TEST_SIZE, GSO_TEST_SIZE, 3 },
>  	},
>  	{
>  		/* commit 3953c46c3ac7 ("sk_buff: allow segmenting based on frag sizes") and

-- 
Kees Cook