From: Joe Perches <joe@perches.com>
To: Alejandro Colomar <alx@kernel.org>, linux-hardening@vger.kernel.org
Cc: Krzysztof Kozlowski <krzk@kernel.org>,
"Maciej W. Rozycki" <macro@orcam.me.uk>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Andreas Schwab <schwab@linux-m68k.org>,
Andy Shevchenko <andy@kernel.org>,
Bartosz Golaszewski <brgl@kernel.org>,
Daniel Scally <djrscally@gmail.com>,
Danilo Krummrich <dakr@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Hans Verkuil <hverkuil-cisco@xs4all.nl>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Johan Hovold <johan@kernel.org>, Kees Cook <kees@kernel.org>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Len Brown <lenb@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linus Walleij <linusw@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Rob Herring <robh@kernel.org>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
Saravana Kannan <saravanak@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Tom Zanussi <zanussi@kernel.org>,
linux-acpi@vger.kernel.org, driver-core@lists.linux.dev,
linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
linux-gpio@vger.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Subject: Re: [PATCH v3 1/5] string: Add strprefix(), and deprecate str_has_prefix()
Date: Tue, 10 Nov 2026 07:47:55 -0800 [thread overview]
Message-ID: <e7b48186a65a759935fdfdc2003b266d05ee2d4c.camel@perches.com> (raw)
In-Reply-To: <556766412884389a7cecfe6affcc9fa3a78f9807.1794323750.git.alx@kernel.org>
On Tue, 2026-11-10 at 16:33 +0100, Alejandro Colomar wrote:
> As Bartosz reported, str_has_prefix() has a bug: it can't differentiate
> between an empty prefix matching an empty string from a non-matching
> prefix. This is a fundamental design flaw in this API, and not
> something that can be fixed.
>
> As always, this is a consequence of choosing sizes instead of pointers.
> Sizes are often the wrong choice. In this specific case, pointers are
> more capable of differentiating these cases, as NULL is a special
> sentinel value that doesn't need to overload a valid value.
>
> Let's implement strprefix(), a function that returns a pointer
> right after the prefix if found, and a null pointer if not found.
>
> We'll slowly migrate existing code from str_has_prefix() to strprefix().
Most uses of str_has_prefix could use the existing strstarts.
next prev parent reply other threads:[~2026-11-10 15:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-10 15:33 [PATCH v3 0/5] Add strprefix() and fix a bug with it Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 1/5] string: Add strprefix(), and deprecate str_has_prefix() Alejandro Colomar
2026-11-10 15:47 ` Joe Perches [this message]
2026-11-10 16:14 ` Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 2/5] device property: Fix fwnode_name_eq() for empty node names Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 3/5] stddef: Add const_cast() Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 4/5] string: Add [C]QChar_of() and QVoid_of() Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 5/5] string: Make strprefix() const-qualifier-generic Alejandro Colomar
2026-11-10 16:32 ` Joe Perches
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