linux-kernel - Re: [PATCHv2] ARM: ioremap: Fix static vm area boundary checking.

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Date:	Fri, 16 May 2014 09:45:44 +0800
From:	Richard Lee <superlibj8301@...il.com>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	iamjoonsoo.kim@....com, santosh.shilimkar@...com,
	linux-arm-kernel@...ts.infradead.org,
	Arnd Bergmann <arnd@...db.de>, Li.Xiubo@...escale.com,
	robherring2@...il.com, linux-kernel@...r.kernel.org,
	lauraa@...eaurora.org
Subject: Re: [PATCHv2] ARM: ioremap: Fix static vm area boundary checking.

On Fri, May 16, 2014 at 1:28 AM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> On Thu, 15 May 2014, Richard Lee wrote:
>
>> Static vm area boundary check:
>>
>>       paddr1 --->|       |
>>                  |       |
>>                  |-------| <-\--- svm->vm->addr(is page aligned)
>>       paddr2 --->|       |    |
>>                  |     --| <--|-- svm->vm->phys_addr
>>                  |       |    |
>>       paddr3 --->|       |    |
>>                  |       |    |
>>                  |-------| <--|-- next page boundary
>>                  |       |    |
>>       paddr4 --->|       |    | <----- svm->vm->size(including guard page)
>>                  |       |    |
>>                  |       |    |
>> max paddr_end -->|-------| <--|-- svm->vm's phys_addr_end
>>                  | ///// |    |
>>       paddr5 --->| guard |    |
>>                  | page  |    |
>>                  | ///// |    |
>>                   -------  <-/--- svm->vm->addr + svm->vm_size
>>
>> <1> If the paddr == paddr1, then continue;
>> <2> If the paddr == paddr2~paddr4 and paddr_end > phys_addr_end,
>>     then continue;
>> <3> if the paddr >= paddr5 then continue;
>>
>> Signed-off-by: Richard Lee <superlibj8301@...il.com>
>
> instead of doing this repeatedly, why not simply ensure the recorded
> static vm information is already page aligned in the first place?
>

Sorry, I'm not very sure what vm information you meant here.

And the 'svm->vm->addr' and 'svm->vm->size' are all page aligned
already, but we cannot make sure that the 'paddr' and
'svm->vm->phys_addr' are page aligned.


Thanks,

BRs
Richard Lee

>
>
>> ---
>>
>>
>> Change in V2:
>>  - PAGE_SIZE --> PAGE_MASK
>>  - remove the 'size' page size align operation.
>>
>>
>>
>>
>>
>>
>>  arch/arm/mm/ioremap.c | 40 ++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 38 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
>> index be69333..f235ab7 100644
>> --- a/arch/arm/mm/ioremap.c
>> +++ b/arch/arm/mm/ioremap.c
>> @@ -47,16 +47,52 @@ static struct static_vm *find_static_vm_paddr(phys_addr_t paddr,
>>  {
>>       struct static_vm *svm;
>>       struct vm_struct *vm;
>> +     size_t offset;
>> +
>> +     offset = paddr & ~PAGE_MASK;
>>
>>       list_for_each_entry(svm, &static_vmlist, list) {
>> +             phys_addr_t paddr_end, phys_addr_end;
>> +             size_t vmoff;
>> +
>>               vm = &svm->vm;
>>               if (!(vm->flags & VM_ARM_STATIC_MAPPING))
>>                       continue;
>>               if ((vm->flags & VM_ARM_MTYPE_MASK) != VM_ARM_MTYPE(mtype))
>>                       continue;
>>
>> -             if (vm->phys_addr > paddr ||
>> -                     paddr + size - 1 > vm->phys_addr + vm->size - 1)
>> +             /* Static vm area boundary check:
>> +              *
>> +              *       paddr1 --->|       |
>> +              *                  |       |
>> +              *                  |-------| <-\--- svm->vm->addr(page aligned)
>> +              *       paddr2 --->|       |    |
>> +              *                  |     --| <--|-- svm->vm->phys_addr
>> +              *                  |       |    |
>> +              *       paddr3 --->|       |    |
>> +              *                  |       |    |
>> +              *                  |-------| <--|-- next page boundary
>> +              *                  |       |    |
>> +              *       paddr4 --->|       |    | <----- svm->vm->size,
>> +              *                  |       |    |         including guard page
>> +              *                  |       |    |
>> +              * max paddr_end -->|-------| <--|-- svm->vm's phys_addr_end
>> +              *                  | ///// |    |
>> +              *       paddr5 --->| guard |    |
>> +              *                  | page  |    |
>> +              *                  | ///// |    |
>> +              *                   -------  <-/-- svm->vm->addr + svm->vm_size
>> +              *
>> +              * <1> If paddr == paddr1, then continue;
>> +              * <2> If paddr == paddr2~paddr4 and paddr_end > phys_addr_end,
>> +              *     then continue;
>> +              * <3> if paddr >= paddr5 then continue;
>> +              */
>> +             vmoff = vm->phys_addr & ~PAGE_MASK;
>> +             phys_addr_end = vm->phys_addr + vm->size - PAGE_SIZE - vmoff;
>> +             paddr_end = paddr + size - offset;
>> +             if (__phys_to_pfn(vm->phys_addr) > __phys_to_pfn(paddr) ||
>> +                     paddr_end - 1 > phys_addr_end - 1)
>>                       continue;
>>
>>               return svm;
>> --
>> 1.8.4
>>
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