Re: [PATCH] mm: debug_page_alloc: fix NULL buf in debug_guardpage_minorder_setup

[John Hubbard]

On 8/5/26 6:56 PM, Ye Liu wrote:
> 
> 
> 在 2026/8/6 09:08, John Hubbard 写道:
>> On 8/5/26 5:45 PM, Ye Liu wrote:
>>> From: Ye Liu <liuye@xxxxxxxxxx>
>>>
>>> If the kernel command line includes "debug_guardpage_minorder" without
>>> an equals sign (i.e., no value is provided), the early parameter
>>> parser passes a NULL buf pointer to the setup function.
>>>
>>> kstrtouint() does not perform a NULL check on its input and calls
>>> directly into kstrtoull() which dereferences s[0] unconditionally,
>>> leading to a NULL pointer dereference and early boot crash.
>>>
>>> Additionally, the error path's pr_err("%s", buf) would also crash with
>>> a NULL format argument.
>>>
>>
>> Maybe a "Fixes:" tag is called for?
>>
> 
> Add the following Fixes. Thanks.
> 
> Fixes: c0a32fc5a2e4 ("mm: more intensive memory corruption debugging")
> 

Looks good,

Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>

thanks,
-- 
John Hubbard

>>
>>> Signed-off-by: Ye Liu <liuye@xxxxxxxxxx>
>>> ---
>>>  mm/debug_page_alloc.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/debug_page_alloc.c b/mm/debug_page_alloc.c
>>> index 41e3d1f1ad96..fd2664c3c86a 100644
>>> --- a/mm/debug_page_alloc.c
>>> +++ b/mm/debug_page_alloc.c
>>> @@ -22,8 +22,8 @@ static int __init debug_guardpage_minorder_setup(char *buf)
>>>  {
>>>  	unsigned int res;
>>>  
>>> -	if (kstrtouint(buf, 10, &res) < 0 ||  res > MAX_PAGE_ORDER / 2) {
>>> -		pr_err("Bad debug_guardpage_minorder value: %s\n", buf);
>>> +	if (!buf || kstrtouint(buf, 10, &res) < 0 || res > MAX_PAGE_ORDER / 2) {
>>> +		pr_err("Bad debug_guardpage_minorder value: %s\n", buf ?: "(missing)");
>>>  		return 0;
>>>  	}
>>>  	_debug_guardpage_minorder = res;
>>
>> thanks,
>