Re: [PATCH] mempool: Use kmalloc_size_roundup() to match ksize() usage

[Vlastimil Babka (SUSE)]

On 10/19/22 07:37, Kees Cook wrote:
> On Tue, Oct 18, 2022 at 03:51:37PM -0700, Andrew Morton wrote:
>> On Tue, 18 Oct 2022 02:03:29 -0700 Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> 
>> > Round up allocations with kmalloc_size_roundup() so that mempool's use
>> > of ksize() is always accurate and no special handling of the memory is
>> > needed by KASAN, UBSAN_BOUNDS, nor FORTIFY_SOURCE.
>> 
>> Confused.  If the special handling is not needed, why doesn't the patch
>> removed the no longer needed special handling?
> 
> The special handling is in the ksize() implementation, so it can't be
> removed[1] until all the ksize()-affected users are updated to see their
> true allocation sizes first.
> 
> [1] https://lore.kernel.org/lkml/20220923202822.2667581-16-keescook@xxxxxxxxxxxx/

But in the previous version I was wondering if we can just stop doing
ksize()-like poison handling in mempool completely, if no mempool consumers
call ksize() to expand their use of the allocated objects. You seemed to
agree but this version is uncahnged?

https://lore.kernel.org/all/f4fc52c4-7c18-1d76-0c7a-4058ea2486b9@xxxxxxx/