From: Kees Cook <kees@kernel.org>
To: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>,
akpm@linux-foundation.org, nathan@kernel.org,
ndesaulniers@google.com, morbo@google.com,
justinstitt@google.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
kernel test robot <lkp@intel.com>
Subject: Re: [PATCH 1/1] alloc_tag: work around clang-14 issue with __builtin_object_size()
Date: Thu, 6 Feb 2025 10:13:21 -0800 [thread overview]
Message-ID: <202502061011.BD9611CEA@keescook> (raw)
In-Reply-To: <jdnvctbd4kfzgjy4s4wpd24zpv66zsn3cjgnsialjbnrl3oa4e@vexb7u4ku2tr>
On Wed, Feb 05, 2025 at 03:16:12PM -0500, Kent Overstreet wrote:
> On Wed, Feb 05, 2025 at 11:18:35AM -0800, Kees Cook wrote:
> > On Sat, Feb 01, 2025 at 12:05:03PM -0800, Suren Baghdasaryan wrote:
> > To Kent's comment[1], I believe I was using __builtin_object_size() here
> > because I have a knee-jerk aversion to sizeof() due to it blowing up on
> > flexible arrays, but that's not relevant here. ARRAY_SIZE() would work,
> > but only if type checking to "char *" succeeds, as Kent suggests.
>
> Yeah, that rational for __builtin_object_size() makes sense - although
> it's not what the gcc docs say, those talk about getting the size from
> an attribute on the allocation function (!).
>
> ARRAY_SIZE() is sizeof() underneath, just used creatively to guarantee
> that the input is an array - although that property is probably what we
> want here, since strtomem_pad() really only makes sense on static or
> flex-arrays, no?
Okay, here's my proposed fix, and confirmed that it solves the problem:
https://lore.kernel.org/lkml/20250206175216.work.225-kees@kernel.org
-Kees
--
Kees Cook
prev parent reply other threads:[~2025-02-06 18:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-01 20:05 Suren Baghdasaryan
2025-02-05 19:18 ` Kees Cook
2025-02-05 19:57 ` Nathan Chancellor
2025-02-05 20:16 ` Kent Overstreet
2025-02-05 21:28 ` Kees Cook
2025-02-06 18:13 ` Kees Cook [this message]
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