Re: [PATCH V3 1/2] mm/ioremap: Check virtual address alignment while creating huge mappings

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 05/14/2019 03:56 AM, Kani, Toshi wrote:
> On Thu, 2019-05-09 at 10:16 +0530, Anshuman Khandual wrote:
>> Virtual address alignment is essential in ensuring correct clearing for all
>> intermediate level pgtable entries and freeing associated pgtable pages. An
>> unaligned address can end up randomly freeing pgtable page that potentially
>> still contains valid mappings. Hence also check it's alignment along with
>> existing phys_addr check.
>>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> Cc: Toshi Kani <toshi.kani@hpe.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Cc: Chintan Pandya <cpandya@codeaurora.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> ---
>>  lib/ioremap.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/lib/ioremap.c b/lib/ioremap.c
>> index 063213685563..8b5c8dda857d 100644
>> --- a/lib/ioremap.c
>> +++ b/lib/ioremap.c
>> @@ -86,6 +86,9 @@ static int ioremap_try_huge_pmd(pmd_t *pmd, unsigned long addr,
>>  	if ((end - addr) != PMD_SIZE)
>>  		return 0;
>>  
>> +	if (!IS_ALIGNED(addr, PMD_SIZE))
>> +		return 0;
>> +
>>  	if (!IS_ALIGNED(phys_addr, PMD_SIZE))
>>  		return 0;
>>  
>> @@ -126,6 +129,9 @@ static int ioremap_try_huge_pud(pud_t *pud, unsigned long addr,
>>  	if ((end - addr) != PUD_SIZE)
>>  		return 0;
>>  
>> +	if (!IS_ALIGNED(addr, PUD_SIZE))
>> +		return 0;
>> +
>>  	if (!IS_ALIGNED(phys_addr, PUD_SIZE))
>>  		return 0;
> 
> Not sure if we have such case today, but I agree that it is prudent to
> have such checks.  Is there any reason not to add this check to p4d for
> consistency?

No, will add it.