linux-kernel - Re: [PATCH] mm/hugetlb: Fix potential double free in hugetlb_register

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Message-Id: <20210107151502.7c581d98078ba90e63553dd4@linux-foundation.org>
Date:   Thu, 7 Jan 2021 15:15:02 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     Miaohe Lin <linmiaohe@...wei.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hugetlb: Fix potential double free in
 hugetlb_register_node() error path

On Thu, 7 Jan 2021 11:59:38 -0800 Mike Kravetz <mike.kravetz@...cle.com> wrote:

> On 1/7/21 4:32 AM, Miaohe Lin wrote:
> > In hugetlb_sysfs_add_hstate(), we would do kobject_put() on hstate_kobjs
> > when failed to create sysfs group but forget to set hstate_kobjs to NULL.
> > Then in hugetlb_register_node() error path, we may free it again via
> > hugetlb_unregister_node().
> > 
> > Fixes: a3437870160c ("hugetlb: new sysfs interface")
> > Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> > Cc: <stable@...r.kernel.org>
> > ---
> >  mm/hugetlb.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> Thanks, this is a potential issue that should be fixed.
> 
> Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
> 
> This has been around for a long time (more than 12 years).  I suspect
> nobody actually experienced this issue.  You just discovered via code
> inspection.  Correct?
> At one time cc stable would not be accepted for this type of issue,
> not sure about today.

sysfs_create_group() will only fail if something is terribly messed up
- probably it has never happened to anyone.  I don't think the
cc:stable is justified here.