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

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Message-ID: <CAM4kBB+v+FJaoKx+zL3pfnV1e1pk8sVRX1=7-aq9OGdXXuBxJA@mail.gmail.com>
Date:   Tue, 23 Jun 2020 16:02:29 +0200
From:   Vitaly Wool <vitaly.wool@...sulko.com>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-kernel@...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 Tue, Jun 23, 2020, 1:12 PM Colin Ian King <colin.king@...onical.com> wrote:
>
> On 22/06/2020 20:55, Song Bao Hua (Barry Song) wrote:
> >
> >
> >> -----Original Message-----
> >> From: Dan Carpenter [mailto:dan.carpenter@...cle.com]
> >> Sent: Tuesday, June 23, 2020 6:28 AM
> >> 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>; Song Bao Hua (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>
> >
> >
> > Colin, thanks for your patch. I am sorry I did the same thing with you here:
> > https://lkml.org/lkml/2020/6/22/347
>
> Thanks for fixing this correctly, I ran out of time yesterday to re-do
> the fix.
>
> Colin

I think this has gotten out of hand. Barry, could you please come up
with a replacement for the initial patch rather than doing it
incrementally?

Thanks,
   Vitaly

>
> >
> >
> >>> ---
> >>>  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
> >
>