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Subject: Re: [PATCH 2/2 V2] livepatch: handle kzalloc failure properly
To:     Nicholas Mc Guire <hofrat@osadl.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>
Cc:     Jessica Yu <jeyu@kernel.org>, Jiri Kosina <jikos@kernel.org>,
        Miroslav Benes <mbenes@suse.cz>,
        Petr Mladek <pmladek@suse.com>, live-patching@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1544709956-16701-1-git-send-email-hofrat@osadl.org>
 <1544709956-16701-2-git-send-email-hofrat@osadl.org>
From:   Joe Lawrence <joe.lawrence@redhat.com>
Organization: Red Hat
Message-ID: <daf5bf66-3bcc-476c-6237-0e46028cb269@redhat.com>
Date:   Thu, 13 Dec 2018 09:14:18 -0500
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On 12/13/2018 09:05 AM, Nicholas Mc Guire wrote:
> kzalloc() return should be checked. On dummy_alloc() failing
> in kzalloc() NULL should be returned.
> 
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
> ---
> 
> Problem was located with an experimental coccinelle script
> 
> V2: returning NULL is ok but not without cleanup - thanks to
>     Petr Mladek <pmladek@suse.com> for catching this.
> 
> Patch was compile tested with: x86_64_defconfig + FTRACE=y
> FUNCTION_TRACER=y, EXPERT=y, LATENCYTOP=y, SAMPLES=y, SAMPLE_LIVEPATCH=y
> (with a number of unrelated sparse warnings on symbols not being static)
> 
> Patch is against 4.20-rc6 (localversion-next is next-20181213)
> 
>  samples/livepatch/livepatch-shadow-mod.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/samples/livepatch/livepatch-shadow-mod.c b/samples/livepatch/livepatch-shadow-mod.c
> index 4c54b25..4aa8a88 100644
> --- a/samples/livepatch/livepatch-shadow-mod.c
> +++ b/samples/livepatch/livepatch-shadow-mod.c
> @@ -118,6 +118,10 @@ noinline struct dummy *dummy_alloc(void)
>  
>  	/* Oops, forgot to save leak! */
>  	leak = kzalloc(sizeof(int), GFP_KERNEL);
> +	if (!leak) {
> +		kfree(d);
> +		return NULL;
> +	}
>  
>  	pr_info("%s: dummy @ %p, expires @ %lx\n",
>  		__func__, d, d->jiffies_expire);
> 

Hi Nicholas,

Thanks for finding and fixing these up... can we either squash these two
patches into a single commit or give them unique subject lines?  Code
looks good (including Petr's suggested fix) otherwise.

-- Joe