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Date: Tue, 24 Feb 2026 23:15:56 -0800
From: Kees Cook <kees@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>, Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Lameter <cl@gentwo.org>,
	David Rientjes <rientjes@google.com>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Harry Yoo <harry.yoo@oracle.com>, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] slab: Saturate to SIZE_MAX for allocation size overflows
Message-ID: <202602242315.C9D5430C7@keescook>
References: <20260225013954.work.319-kees@kernel.org>
 <aZ5zjIpYZYoc-LSX@casper.infradead.org>
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In-Reply-To: <aZ5zjIpYZYoc-LSX@casper.infradead.org>

On Wed, Feb 25, 2026 at 03:59:08AM +0000, Matthew Wilcox wrote:
> On Tue, Feb 24, 2026 at 05:40:02PM -0800, Kees Cook wrote:
> > +++ b/include/linux/slab.h
> > @@ -1105,7 +1105,7 @@ static inline __alloc_size(1, 2) void *kmalloc_array_noprof(size_t n, size_t siz
> >  	size_t bytes;
> >  
> >  	if (unlikely(check_mul_overflow(n, size, &bytes)))
> > -		return NULL;
> > +		bytes = SIZE_MAX;
> >  	return kmalloc_noprof(bytes, flags);
> 
> Wouldn't this be better written as:
> 
> 	return kmalloc_noprof(size_mul(n, size), flags);
> 
> (etc)

Sure, I can convert them all that way if that's preferred?

-- 
Kees Cook