Re: [PATCH] mm: add stack trace when bad rss-counter state is detected

[Xuanye Liu]

在 2025/7/23 15:31, Kees Cook 写道:
> On Wed, Jul 23, 2025 at 03:23:49PM +0800, Xuanye Liu wrote:
>> The check_mm() function verifies the correctness of rss counters in
>> struct mm_struct. Currently, it only prints an alert when a bad
>> rss-counter state is detected, but lacks sufficient context for
>> debugging.
>>
>> This patch adds a dump_stack() call to provide a stack trace when
>> the rss-counter state is invalid. This helps developers identify
>> where the corrupted mm_struct is being checked and trace the
>> underlying cause of the inconsistency.
> Why not just convert the pr_alert to a WARN?
Good idea! I'll gather more feedback from others and then update to v2.
>
> -Kees
>
>> Signed-off-by: Xuanye Liu <liuqiye2025@xxxxxxx>
>> ---
>>  kernel/fork.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/fork.c b/kernel/fork.c
>> index cfe2f1df5f27..d38f1c5270ea 100644
>> --- a/kernel/fork.c
>> +++ b/kernel/fork.c
>> @@ -584,9 +584,11 @@ static void check_mm(struct mm_struct *mm)
>>  	for (i = 0; i < NR_MM_COUNTERS; i++) {
>>  		long x = percpu_counter_sum(&mm->rss_stat[i]);
>>  
>> -		if (unlikely(x))
>> +		if (unlikely(x)) {
>>  			pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
>>  				 mm, resident_page_types[i], x);
>> +			dump_stack();
>> +		}
>>  	}
>>  
>>  	if (mm_pgtables_bytes(mm))
>> -- 
>> 2.43.0
>>
-- 
Thanks,
Xuanye