From: Kees Cook <kees@kernel.org>
To: Karl Mehltretter <kmehltretter@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>, Harry Yoo <harry@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Hao Li <hao.li@linux.dev>, Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Catalin Marinas <catalin.marinas@arm.com>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
linux-hardening@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v2 2/3] slab: check for ZERO_SIZE_PTR by exact match
Date: Tue, 11 Aug 2026 17:17:48 -0700 [thread overview]
Message-ID: <202608111716.0FA9DB17@keescook> (raw)
In-Reply-To: <20260811141240.62519-3-kmehltretter@gmail.com>
On Tue, Aug 11, 2026 at 04:12:39PM +0200, Karl Mehltretter wrote:
> ZERO_OR_NULL_PTR() returns true for every value less than or equal to
> ZERO_SIZE_PTR. With the sentinel raised to ARCH_KMALLOC_MINALIGN, up
> to 128 on some architectures, the helper matches additional values
> that are neither NULL nor the sentinel.
>
> Compare explicitly against NULL and ZERO_SIZE_PTR. Store the argument
> in an unsigned long temporary to support both pointer and integer
> address arguments while evaluating it only once.
Can we move ZERO_SIZE_PTR to cover the ERR_PTR range too? See this issue:
https://github.com/KSPP/linux/issues/93
> This also changes check_bogus_address() in hardened usercopy: nonzero
> addresses below ZERO_SIZE_PTR no longer cause its null-address abort.
And then check_bogus_address would also catch ERR_PTR.
-Kees
--
Kees Cook
next prev parent reply other threads:[~2026-08-12 0:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-11 14:12 [PATCH v2 0/3] slab: ZERO_SIZE_PTR alignment and exact matching Karl Mehltretter
2026-08-11 14:12 ` [PATCH v2 1/3] slab: align ZERO_SIZE_PTR to ARCH_KMALLOC_MINALIGN Karl Mehltretter
2026-08-11 14:12 ` [PATCH v2 2/3] slab: check for ZERO_SIZE_PTR by exact match Karl Mehltretter
2026-08-12 0:17 ` Kees Cook [this message]
2026-08-11 14:12 ` [PATCH v2 3/3] slab: test zero-size allocations in slub_kunit Karl Mehltretter
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