linux-hardening - Re: [PATCH v4 01/10] string: provide strends()

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Message-ID: <CAMRc=Mekr=xcGbSBD583nUqR43aLYO9iGakbOSSFEWYdbXW73Q@mail.gmail.com>
Date: Tue, 18 Nov 2025 10:47:09 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Kees Cook <kees@...nel.org>
Cc: Mika Westerberg <westeri@...nel.org>, Dmitry Torokhov <dmitry.torokhov@...il.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Linus Walleij <linus.walleij@...aro.org>, 
	Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Andy Shevchenko <andy@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Srinivas Kandagatla <srini@...nel.org>, Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>, 
	Alexey Klimov <alexey.klimov@...aro.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, linux-hardening@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sound@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v4 01/10] string: provide strends()

On Mon, Nov 17, 2025 at 9:33 PM Kees Cook <kees@...nel.org> wrote:
>
> On Wed, Nov 12, 2025 at 02:55:30PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > Implement a function for checking if a string ends with a different
> > string and add its kunit test cases.
> >
> > Acked-by: Linus Walleij <linus.walleij@...aro.org>
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---

Hi Kees!

Thanks for the review. I already queued this for v6.19, so let me
address the issues in a follow-up.

> >  include/linux/string.h   | 18 ++++++++++++++++++
> >  lib/tests/string_kunit.c | 13 +++++++++++++
> >  2 files changed, 31 insertions(+)
> >
> > diff --git a/include/linux/string.h b/include/linux/string.h
> > index fdd3442c6bcbd786e177b6e87358e1065a0ffafc..929d05d1247c76eb9011fe34250b487834b2d3c9 100644
> > --- a/include/linux/string.h
> > +++ b/include/linux/string.h
> > @@ -562,4 +562,22 @@ static inline bool strstarts(const char *str, const char *prefix)
> >       return strncmp(str, prefix, strlen(prefix)) == 0;
> >  }
> >
> > +/**
> > + * strends - Check if a string ends with another string.
> > + * @str - NULL-terminated string to check against @suffix
> > + * @suffix - NULL-terminated string defining the suffix to look for in @str
> > + *
> > + * Returns:
> > + * True if @str ends with @suffix. False in all other cases.
>
> Maybe added "empty strings never match"?
>

But they do, please see the test.

> > + */
> > +static inline bool strends(const char *str, const char *suffix)
>
> These are required to be non-NULL, so we might want to consider marking
> them as such with the "nonnull" attribute. We don't use it much in Linux
> yet, but I do see a few places.
>
> e.g.:
>
> static inline bool __attribute__((nonnull(1,2)))
> strends(const char *str, const char *suffix)
>

Ok.

> > +{
> > +     unsigned int str_len = strlen(str), suffix_len = strlen(suffix);
> > +
> > +     if (str_len < suffix_len)
> > +             return false;
> > +
> > +     return !(strcmp(str + str_len - suffix_len, suffix));
> > +}
>
> We should probably add it to strlen and strcmp as well. :)
>

Sure but that's outside of the scope of this.

Bart