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Message-ID: <a9c6c111-d92f-f76f-1b7a-f6220d755eeb@kernel.org>
Date:   Mon, 24 Oct 2022 20:03:34 +0200
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Subject: Re: [PATCH] mempool: Use kmalloc_size_roundup() to match ksize()
 usage
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To:     Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org
References: <20221018090323.never.897-kees@kernel.org>
 <20221018155137.f6898d165aade2e3a5f0b2d3@linux-foundation.org>
 <202210182235.3B19DFCB28@keescook>
From:   "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
In-Reply-To: <202210182235.3B19DFCB28@keescook>
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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@chromium.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/