From mboxrd@z Thu Jan  1 00:00:00 1970
From: Florian Westphal <fw@strlen.de>
Subject: Re: [PATCH] iptables: set errno correctly in
 iptcc_chain_index_alloc
Date: Thu, 4 Jul 2013 18:33:25 +0200
Message-ID: <20130704163325.GD2351@breakpoint.cc>
References: <20130704011610.GA9791@linuxace.com>
 <20130704074222.GC2351@breakpoint.cc>
 <20130704161845.GA11465@linuxace.com>
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Cc: Florian Westphal <fw@strlen.de>, netfilter-devel@vger.kernel.org,
	pablo@netfilter.org
To: Phil Oester <kernel@linuxace.com>
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Phil Oester <kernel@linuxace.com> wrote:
> Simulate an out of memory condition with this patch
> 
> @@ -500,9 +500,11 @@ static int iptcc_chain_index_alloc(struct xtc_handle *h)
>               array_elems, array_mem);
> 
>         h->chain_index = malloc(array_mem);
> -       if (h->chain_index == NULL && array_mem > 0) {
> +       //if (h->chain_index == NULL && array_mem > 0) {
> +       if (1) {
>                 h->chain_index_sz = 0;
> With the patch, the error message returned to user:
> 
>    ...can't initialize iptables table `filter': Memory allocation problem
> 
> without the patch:
> 
>    ...can't initialize iptables table `filter': Incompatible with this kernel
> 
> The former seems better, no?

Yes, but malloc didn't fail, so malloc didn't set errno.

My point is, that we should not muck with errno, especially
after libc functions that usually already set it on error.