netdev - Re: [PATCH ethtool v2 11/13] ethtool: fix missing free of memory after failure

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Message-ID: <20221208105247.vpb5aqn6hp3unjqx@lion.mk-sys.cz>
Date:   Thu, 8 Dec 2022 11:52:47 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH ethtool v2 11/13] ethtool: fix missing free of memory
 after failure

On Wed, Dec 07, 2022 at 05:11:20PM -0800, Jesse Brandeburg wrote:
> cppcheck warns:
> test-common.c:106:2: error: Common realloc mistake: 'block' nulled but not freed upon failure [memleakOnRealloc]
>  block = realloc(block, sizeof(*block) + size);
>  ^
> 
> Fix the issue by storing a local copy of the old pointer and using that
> to free the original if the realloc fails, as the manual for realloc()
> suggests.
> 
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>

Acked-by: Michal Kubecek <mkubecek@...e.cz>

> ---
>  test-common.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/test-common.c b/test-common.c
> index e4dac3298577..b472027140f6 100644
> --- a/test-common.c
> +++ b/test-common.c
> @@ -97,15 +97,18 @@ void test_free(void *ptr)
>  
>  void *test_realloc(void *ptr, size_t size)
>  {
> -	struct list_head *block = NULL;
> +	struct list_head *block = NULL, *oldblock;
>  
>  	if (ptr) {
>  		block = (struct list_head *)ptr - 1;
>  		list_del(block);
>  	}
> -	block = realloc(block, sizeof(*block) + size);
> -	if (!block)
> +	oldblock = block;
> +	block = realloc(oldblock, sizeof(*oldblock) + size);
> +	if (!block) {
> +		free(oldblock);
>  		return NULL;
> +	}
>  	list_add(block, &malloc_list);
>  	return block + 1;
>  }
> -- 
> 2.31.1
> 

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