On 11/12/2015 04:55 PM, Andrey Ryabinin wrote:
> 2015-11-12 18:17 GMT+03:00 Jerome Marchand <jmarchan@xxxxxxxxxx>:
>> Commit 71394fe50146 ("mm: vmalloc: add flag preventing guard hole
>> allocation") missed a spot. Currently remove_vm_area() decreases
>> vm->size to remove the guard hole page, even when it isn't present.
>> This patch only decreases vm->size when VM_NO_GUARD isn't set.
>>
>> Signed-off-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
>> ---
>> mm/vmalloc.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index d045634..1388c3d 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -1443,7 +1443,8 @@ struct vm_struct *remove_vm_area(const void *addr)
>> vmap_debug_free_range(va->va_start, va->va_end);
>> kasan_free_shadow(vm);
>> free_unmap_vmap_area(va);
>> - vm->size -= PAGE_SIZE;
>> + if (!(vm->flags & VM_NO_GUARD))
>> + vm->size -= PAGE_SIZE;
>>
>
> I'd fix this in another way. I think that remove_vm_area() shouldn't
> change vm's size, IMO it doesn't make sense.
> The only caller who cares about vm's size after removing is __vunmap():
> area = remove_vm_area(addr);
> ....
> debug_check_no_locks_freed(addr, area->size);
> debug_check_no_obj_freed(addr, area->size);
>
> We already have proper get_vm_area_size() helper which takes
> VM_NO_GUARD into account.
> So I think we should use that helper for debug_check_no_*() and just
> remove 'vm->size -= PAGE_SIZE;' line
> from remove_vm_area()
Sure, that would be cleaner.
Btw, there might be a leak in sq_unmap() (arch/sh/kernel/cpu/sh4/sq.c)
as the vm_struct doesn't seem to be freed. CCed the SuperH folks.
Thanks,
Jerome
>
>
>
>> return vm;
>> }
>> --
>> 2.4.3
>>
Attachment:
signature.asc
Description: OpenPGP digital signature