From: Kees Cook <kees@kernel.org>
To: david.laight.linux@gmail.com
Cc: linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH next 2/3] fortify: Optimise strnlen()
Date: Mon, 30 Mar 2026 23:36:07 -0700 [thread overview]
Message-ID: <202603302335.0AEEF9154@keescook> (raw)
In-Reply-To: <20260330132003.3379-3-david.laight.linux@gmail.com>
On Mon, Mar 30, 2026 at 02:20:02PM +0100, david.laight.linux@gmail.com wrote:
> From: David Laight <david.laight.linux@gmail.com>
>
> If the string is constant there is no need to call __real_strlen()
> even when maxlen is a variable - just return the smaller value.
>
> If the size of the string variable is unknown fortify_panic() can't be
> called, change the condition so that the compiler can optimise it away.
>
> Change __compiletime_strlen(p) to return a 'non-constant' value
> for non-constant strings (the same as __builtin_strlen()).
> Simplify since it is only necessary to check that the size is constant
> and that the last character is '\0'.
> Explain why it is different from __builtin_strlen().
> Update the kunit tests to match.
See also
commit d07c0acb4f41 ("fortify: Fix __compiletime_strlen() under UBSAN_BOUNDS_LOCAL")
-Kees
--
Kees Cook
next prev parent reply other threads:[~2026-03-31 6:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-30 13:20 [PATCH next 0/3] fortify: Minor changes to strlen() and strnlen() david.laight.linux
2026-03-30 13:20 ` [PATCH next 1/3] fortify: replace __compiletime_lessthan() with statically_true() david.laight.linux
2026-03-30 23:50 ` Kees Cook
2026-03-30 13:20 ` [PATCH next 2/3] fortify: Optimise strnlen() david.laight.linux
2026-03-30 23:54 ` Kees Cook
2026-03-31 22:09 ` David Laight
2026-03-31 23:51 ` Kees Cook
2026-04-01 13:48 ` David Laight
2026-04-03 8:50 ` David Laight
2026-03-31 6:36 ` Kees Cook [this message]
2026-03-31 10:14 ` David Laight
2026-03-31 14:55 ` David Laight
2026-03-31 15:56 ` Kees Cook
2026-04-01 0:15 ` kernel test robot
2026-04-03 8:23 ` David Laight
2026-03-30 13:20 ` [PATCH next 3/3] fortify: Simplify strlen() logic david.laight.linux
2026-03-31 6:07 ` Kees Cook
2026-03-31 8:58 ` David Laight
2026-03-31 6:18 ` Kees Cook
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