linux-kernel - Re: [PATCH 2/2] mm: vmalloc: Pass proper vm

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Message-Id: <e8d4c0b2-dfb5-8d4d-3bcc-30b8915d24cb@linux.vnet.ibm.com>
Date:   Tue, 17 Apr 2018 08:39:36 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Chintan Pandya <cpandya@...eaurora.org>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        vbabka@...e.cz, labbott@...hat.com, catalin.marinas@....com,
        hannes@...xchg.org, f.fainelli@...il.com, xieyisheng1@...wei.com,
        ard.biesheuvel@...aro.org, richard.weiyang@...il.com,
        byungchul.park@....com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: vmalloc: Pass proper vm_start into debugobjects

On 04/16/2018 05:39 PM, Chintan Pandya wrote:
> 
> 
> On 4/13/2018 5:31 PM, Anshuman Khandual wrote:
>> On 04/13/2018 05:03 PM, Chintan Pandya wrote:
>>> Client can call vunmap with some intermediate 'addr'
>>> which may not be the start of the VM area. Entire
>>> unmap code works with vm->vm_start which is proper
>>> but debug object API is called with 'addr'. This
>>> could be a problem within debug objects.
>>>
>>> Pass proper start address into debug object API.
>>>
>>> Signed-off-by: Chintan Pandya <cpandya@...eaurora.org>
>>> ---
>>>   mm/vmalloc.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>>> index 9ff21a1..28034c55 100644
>>> --- a/mm/vmalloc.c
>>> +++ b/mm/vmalloc.c
>>> @@ -1526,8 +1526,8 @@ static void __vunmap(const void *addr, int
>>> deallocate_pages)
>>>           return;
>>>       }
>>>   -    debug_check_no_locks_freed(addr, get_vm_area_size(area));
>>> -    debug_check_no_obj_freed(addr, get_vm_area_size(area));
>>> +    debug_check_no_locks_freed(area->addr, get_vm_area_size(area));
>>> +    debug_check_no_obj_freed(area->addr, get_vm_area_size(area));
>>
>> This kind of makes sense to me but I am not sure. We also have another
>> instance of this inside the function vm_unmap_ram() where we call for
> Right, I missed it. I plan to add below stub in v2.
> 
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1124,15 +1124,15 @@ void vm_unmap_ram(const void *mem, unsigned int
> count)
>         BUG_ON(addr > VMALLOC_END);
>         BUG_ON(!PAGE_ALIGNED(addr));
> 
> -       debug_check_no_locks_freed(mem, size);
> -
>         if (likely(count <= VMAP_MAX_ALLOC)) {
> +               debug_check_no_locks_freed(mem, size);

It should have been 'va->va_start' instead of 'mem' in here but as
said before it looks correct to me but I am not really sure.