linux-kernel - Re: [PATCH] mempool: Use kmalloc_size

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Message-ID: <a9c6c111-d92f-f76f-1b7a-f6220d755eeb@kernel.org>
Date:   Mon, 24 Oct 2022 20:03:34 +0200
From:   "Vlastimil Babka (SUSE)" <vbabka@...nel.org>
To:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] mempool: Use kmalloc_size_roundup() to match ksize()
 usage

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@...omium.org> 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@chromium.org/

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@suse.cz/