linux-kernel - Re: [PATCH][next] mm/zswap: fix a couple of memory leaks and rework kzalloc failure check

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Date:   Mon, 22 Jun 2020 21:28:17 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        Vitaly Wool <vitaly.wool@...sulko.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>, linux-mm@...ck.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] mm/zswap: fix a couple of memory leaks and rework
 kzalloc failure check

On Mon, Jun 22, 2020 at 04:35:46PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> kzalloc failures return NULL on out of memory errors, so replace the
> IS_ERR_OR_NULL check with the usual null pointer check.  Fix two memory
> leaks with on acomp and acomp_ctx by ensuring these objects are free'd
> on the error return path.
> 
> Addresses-Coverity: ("Resource leak")
> Fixes: d4f86abd6e35 ("mm/zswap: move to use crypto_acomp API for hardware acceleration")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  mm/zswap.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 0d914ba6b4a0..14839cbac7ff 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -433,23 +433,23 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
>  		return 0;
>  
>  	acomp_ctx = kzalloc(sizeof(*acomp_ctx), GFP_KERNEL);
> -	if (IS_ERR_OR_NULL(acomp_ctx)) {
> +	if (!acomp_ctx) {
>  		pr_err("Could not initialize acomp_ctx\n");
>  		return -ENOMEM;
>  	}
>  	acomp = crypto_alloc_acomp(pool->tfm_name, 0, 0);
> -	if (IS_ERR_OR_NULL(acomp)) {
> +	if (!acomp) {

This should be IS_ERR(acomp).  Please preserve the error code.

>  		pr_err("could not alloc crypto acomp %s : %ld\n",
>  				pool->tfm_name, PTR_ERR(acomp));
> -		return -ENOMEM;
> +		goto free_acomp_ctx;
>  	}
>  	acomp_ctx->acomp = acomp;
>  
>  	req = acomp_request_alloc(acomp_ctx->acomp);
> -	if (IS_ERR_OR_NULL(req)) {
> +	if (!req) {
>  		pr_err("could not alloc crypto acomp %s : %ld\n",
>  		       pool->tfm_name, PTR_ERR(acomp));
> -		return -ENOMEM;
> +		goto free_acomp;
>  	}
>  	acomp_ctx->req = req;
>  
> @@ -462,6 +462,12 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
>  	*per_cpu_ptr(pool->acomp_ctx, cpu) = acomp_ctx;
>  
>  	return 0;
> +
> +free_acomp:
> +	kfree(acomp);

The kfree() isn't correct.  It needs to be:

	crypto_free_acomp(acomp);

> +free_acomp_ctx:
> +	kfree(acomp_ctx);
> +	return -ENOMEM;

regards,
dan carpenter