Re: [PATCH v2 2/2] mm: usercopy: Warn vmalloc/module address in check_heap_object()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2021/12/27 1:33, Christophe Leroy wrote:
>
> Le 25/12/2021 à 13:06, Kefeng Wang a écrit :
>> virt_addr_valid() could be insufficient to validate the virt addr
>> on some architecture, which could lead to potential BUG which has
>> been found on arm64/powerpc64.
>>
>> Let's add WARN_ON to check if the virt addr is passed virt_addr_valid()
>> but is a vmalloc/module address.
> I think that's the responsibility of the architecture and doesn't
> deserve a WARN_ON() in generic code.
>
> The generic code cannot check all what architectures do wrong.
>
> Eventually you can do some testing at startup, maybe with
> CONFIG_DEBUG_VM_PGTABLE, but I don't think we should have such
> verification in functions like check_heap_object()

Ok, we could find other better place to add a virt_to_valid() check

instead of this one.

>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>>    mm/usercopy.c | 2 ++
>>    1 file changed, 2 insertions(+)
>>
>> diff --git a/mm/usercopy.c b/mm/usercopy.c
>> index b3de3c4eefba..ce83e0b137dd 100644
>> --- a/mm/usercopy.c
>> +++ b/mm/usercopy.c
>> @@ -228,6 +228,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
>>    	if (!virt_addr_valid(ptr))
>>    		return;
>>    
>> +	WARN_ON_ONCE(is_vmalloc_or_module_addr(ptr));
>> +
>>    	/*
>>    	 * When CONFIG_HIGHMEM=y, kmap_to_page() will give either the
>>    	 * highmem page or fallback to virt_to_page(). The following