From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: Bradley Morgan <include@grrlz.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <kees@kernel.org>, Andy Shevchenko <andy@kernel.org>,
Akinobu Mita <akinobu.mita@gmail.com>,
Joern Engel <joern@logfs.org>, Pekka Enberg <penberg@kernel.org>,
Christoph Lameter <cl@linux-foundation.org>,
linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] lib/string: fix memchr_inv() for large ranges
Date: Tue, 23 Jun 2026 23:54:55 +0300 [thread overview]
Message-ID: <ajrynyaEVnTNEN13@ashevche-desk.local> (raw)
In-Reply-To: <20260621121133.16460-1-include@grrlz.net>
On Sun, Jun 21, 2026 at 12:11:33PM +0000, Bradley Morgan wrote:
> memchr_inv() takes a size_t length but counts 8 byte words in an
> unsigned int. At 32GiB that count wraps, so the scan can quietly miss
> most of the range.
Wow! Is it real life use case?
> Use size_t for the word count.
...
> @@ -837,7 +837,8 @@ void *memchr_inv(const void *start, int c, size_t bytes)
> {
> u8 value = c;
> u64 value64;
> - unsigned int words, prefix;
> + size_t words;
> + unsigned int prefix;
Perhaps move towards reversed xmas tree while at it?
unsigned int prefix;
size_t words;
u8 value = c;
u64 value64;
(same lines touched, no extra).
> if (bytes <= 16)
> return check_bytes8(start, value, bytes);
--
With Best Regards,
Andy Shevchenko
prev parent reply other threads:[~2026-06-23 20:55 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-21 12:11 Bradley Morgan
2026-06-23 20:54 ` Andy Shevchenko [this message]
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