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

[Ye Liu <ye.liu@linux.dev>]

在 2026/8/6 09:08, John Hubbard 写道:
> On 8/5/26 5:45 PM, Ye Liu wrote:
>> From: Ye Liu <liuye@kylinos.cn>
>>
>> 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")

> 
>> Signed-off-by: Ye Liu <liuye@kylinos.cn>
>> ---
>>  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,

-- 
Thanks,
Ye Liu