RE: [PATCH][next] mm/zswap: fix a couple of memory leaks and rework kzalloc failure check

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: Dan Carpenter [mailto:dan.carpenter@xxxxxxxxxx]
> Sent: Tuesday, June 23, 2020 6:28 AM
> To: Colin King <colin.king@xxxxxxxxxxxxx>
> Cc: Seth Jennings <sjenning@xxxxxxxxxx>; Dan Streetman
> <ddstreet@xxxxxxxx>; Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>; Andrew
> Morton <akpm@xxxxxxxxxxxxxxxxxxxx>; Song Bao Hua (Barry Song)
> <song.bao.hua@xxxxxxxxxxxxx>; Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>;
> linux-mm@xxxxxxxxx; kernel-janitors@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> 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@xxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxx>


Colin, thanks for your patch. I am sorry I did the same thing with you here:
https://lkml.org/lkml/2020/6/22/347


> > ---
> >  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