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

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Message-ID: <202210182235.3B19DFCB28@keescook>
Date:   Tue, 18 Oct 2022 22:37:07 -0700
From:   Kees Cook <keescook@...omium.org>
To:     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 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/

-- 
Kees Cook