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

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Message-ID: <0c53d7a7-df61-9187-676b-6ba5d0829394@huawei.com>
Date:   Fri, 8 Jan 2021 09:41:01 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
CC:     <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 2021/1/8 7:15, Andrew Morton wrote:
> 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?

Yes, I found this by code inspection.

>> 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.
> 
> .
> 

I would take care of more when cc stable. Many thanks for both of you!