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

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

[Ye Liu]

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.

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;
-- 
2.25.1

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

[Zi Yan]

On Wed Aug 5, 2026 at 8:45 PM EDT, 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.
>
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> ---
>  mm/debug_page_alloc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
LGTM.

Acked-by: Zi Yan <ziy@nvidia.com>


-- 
Best Regards,
Yan, Zi

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

[John Hubbard]

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?


> 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,
-- 
John Hubbard

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

[Ye Liu]

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

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@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")
> 

Looks good,

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
-- 
John Hubbard

>>
>>> 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,
>