linux-kernel - Re: [updated PATCH] Close mem leak in error path in mm/hugetlb.c::nr_hugepages_store

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Message-ID: <AANLkTikmKB+4vP-dox+T0QzF-yTz7LQrTURYMcqHShsa@mail.gmail.com>
Date:	Tue, 21 Dec 2010 08:38:23 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [updated PATCH] Close mem leak in error path in mm/hugetlb.c::nr_hugepages_store_common()

On Tue, Dec 21, 2010 at 7:05 AM, Jesper Juhl <jj@...osbits.net> wrote:
> On Mon, 20 Dec 2010, Minchan Kim wrote:
>
>> On Mon, Dec 20, 2010 at 7:10 AM, Jesper Juhl <jj@...osbits.net> wrote:
>> > Hi,
>> >
>> > The NODEMASK_ALLOC macro dynamically allocates memory for its second
>> > argument ('nodes_allowed' in this context).
>> > In nr_hugepages_store_common() we may abort early if strict_strtoul()
>> > fails, but in that case we do not free the memory already allocated to
>> > 'nodes_allowed', causing a memory leak.
>> > This patch closes the leak by freeing the memory in the error path.
>> >
>> >
>> > Signed-off-by: Jesper Juhl <jj@...osbits.net>
>> > ---
>> >  hugetlb.c |    4 +++-
>> >  1 file changed, 3 insertions(+), 1 deletion(-)
>> >
>> >  compile tested only
>> >
>> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> > index 8585524..9fdcc35 100644
>> > --- a/mm/hugetlb.c
>> > +++ b/mm/hugetlb.c
>> > @@ -1439,8 +1439,10 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
>> >        NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
>> >
>> >        err = strict_strtoul(buf, 10, &count);
>> > -       if (err)
>> > +       if (err) {
>> > +               kfree(nodes_allowed);
>>
>> Nice catch. But use NODEMASK_FREE. It might be not kmalloced object.
>>
> Right. I just checked the macro and it used kmalloc(), so I just wrote
> kfree. But you are right, NODEMASK_FREE is the right thing to use here.
> Updated patch below.
>
>
> Signed-off-by: Jesper Juhl <jj@...osbits.net>
Reviewed-by: Minchan Kim <minchan.kim@...il.com>

Could you resend the completed patch to save Andrew trouble?


-- 
Kind regards,
Minchan Kim
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