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From: Karl Mehltretter <kmehltretter@gmail.com>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: 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>,
	Kees Cook <kees@kernel.org>,
	 "Gustavo A . R . Silva" <gustavoars@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Shuah Khan <shuah@kernel.org>,
	 Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	 Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	 linux-hardening@vger.kernel.org, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org,  linux-kernel@vger.kernel.org,
	llvm@lists.linux.dev
Subject: Re: [PATCH v3 3/5] slab: handle ERR_PTR values in kfree and hardened usercopy
Date: Sat, 19 Sep 2026 11:39:47 +0200	[thread overview]
Message-ID: <aq5YL3P6tuFy4eTU@gmail.com> (raw)
In-Reply-To: <497a85d3-e062-4930-bcb8-c86a8205e7b2@kernel.org>

> > +	if (WARN_ON(IS_ERR(object)))
> 
> Wonder if WARN_ON_ONCE() would be better.
> Also wonder about the benefits for hardening (as opposed to debugging).
> Without this check it would fault. Now it warns, but hardened setups often
> use panic_on_warn anyway, so the result is the same?
> 

Yes, I'll switch to WARN_ON_ONCE().

You're right about panic_on_warn. The benefit is a clearer diagnostic
and, when warnings aren't fatal, returning before virt_to_page().

I'll split out the ERR_PTR patches as Harry suggested and recheck the
KUnit warning-count test with WARN_ON_ONCE().

Thanks,
Karl

  reply	other threads:[~2026-09-19  9:39 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-03 20:37 [PATCH v3 0/5] slab: ZERO_SIZE_PTR alignment and ERR_PTR hardening Karl Mehltretter
2026-09-03 20:37 ` [PATCH v3 1/5] slab: align ZERO_SIZE_PTR to ARCH_KMALLOC_MINALIGN Karl Mehltretter
2026-09-19 10:41   ` David Laight
2026-09-03 20:37 ` [PATCH v3 2/5] slab: check for ZERO_SIZE_PTR by exact match Karl Mehltretter
2026-09-03 20:37 ` [PATCH v3 3/5] slab: handle ERR_PTR values in kfree and hardened usercopy Karl Mehltretter
2026-09-04  9:01   ` Vlastimil Babka (SUSE)
2026-09-19  9:39     ` Karl Mehltretter [this message]
2026-09-19 11:04   ` David Laight
2026-09-03 20:37 ` [PATCH v3 4/5] slab: test zero-size allocations in slub_kunit Karl Mehltretter
2026-09-03 20:37 ` [PATCH v3 5/5] slab: test ERR_PTR handling in kfree and hardened usercopy Karl Mehltretter
2026-09-04 11:25 ` [PATCH v3 0/5] slab: ZERO_SIZE_PTR alignment and ERR_PTR hardening Harry Yoo
2026-09-19  9:07   ` Karl Mehltretter

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