linux-hardening - Re: [PATCH] thermal: intel: int340x_thermal: replace deprecated strncpy with strscpy

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Date: Tue, 19 Mar 2024 09:20:26 -0700
From: srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Justin Stitt
	 <justinstitt@...gle.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui
 <rui.zhang@...el.com>,  Lukasz Luba <lukasz.luba@....com>,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] thermal: intel: int340x_thermal: replace deprecated
 strncpy with strscpy

On Tue, 2024-03-19 at 12:39 +0100, Rafael J. Wysocki wrote:
> On Mon, Mar 18, 2024 at 11:36 PM Justin Stitt
> <justinstitt@...gle.com> wrote:
> > 
> > strncpy() is deprecated for use on NUL-terminated destination
> > strings
> > [1] and as such we should prefer more robust and less ambiguous
> > string
> > interfaces.
> > 
> > psvt->limit.string can only be 8 bytes so let's use the appropriate
> > size
> > macro ACPI_LIMIT_STR_MAX_LEN.
> > 
> > Neither psvt->limit.string or psvt_user[i].limit.string requires
> > the
> > NUL-padding behavior that strncpy() provides as they have both been
> > filled with NUL-bytes prior to the string operation.
> > >       memset(&psvt->limit, 0, sizeof(u64));
> > and
> > >       psvt_user = kzalloc(psvt_len, GFP_KERNEL);
> > 
> > Let's use `strscpy` [2] due to the fact that it guarantees
> > NUL-termination on the destination buffer without unnecessarily
> > NUL-padding.
> > 
> > Link:
> > https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> >  [1]
> > Link:
> > https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
> >  [2]
> > Link: https://github.com/KSPP/linux/issues/90
> > Cc: linux-hardening@...r.kernel.org
> > Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> 
> Srinivas, any objections?
No

Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>

> 
> > ---
> > Note: build-tested only.
> > 
> > Found with: $ rg "strncpy\("
> > ---
> >  drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git
> > a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
> > b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
> > index dc519a665c18..4b4a4d63e61f 100644
> > --- a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
> > +++ b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
> > @@ -309,7 +309,7 @@ static int acpi_parse_psvt(acpi_handle handle,
> > int *psvt_count, struct psvt **ps
> > 
> >                 if (knob->type == ACPI_TYPE_STRING) {
> >                         memset(&psvt->limit, 0, sizeof(u64));
> > -                       strncpy(psvt->limit.string, psvt_ptr-
> > >limit.str_ptr, knob->string.length);
> > +                       strscpy(psvt->limit.string, psvt_ptr-
> > >limit.str_ptr, ACPI_LIMIT_STR_MAX_LEN);
> >                 } else {
> >                         psvt->limit.integer = psvt_ptr-
> > >limit.integer;
> >                 }
> > @@ -468,7 +468,7 @@ static int fill_psvt(char __user *ubuf)
> >                 psvt_user[i].unlimit_coeff =
> > psvts[i].unlimit_coeff;
> >                 psvt_user[i].control_knob_type =
> > psvts[i].control_knob_type;
> >                 if (psvt_user[i].control_knob_type ==
> > ACPI_TYPE_STRING)
> > -                       strncpy(psvt_user[i].limit.string,
> > psvts[i].limit.string,
> > +                       strscpy(psvt_user[i].limit.string,
> > psvts[i].limit.string,
> >                                 ACPI_LIMIT_STR_MAX_LEN);
> >                 else
> >                         psvt_user[i].limit.integer =
> > psvts[i].limit.integer;
> > 
> > ---
> > base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400
> > change-id: 20240318-strncpy-drivers-thermal-intel-int340x_thermal-
> > acpi_thermal_rel-c-17070c1e42f3
> > 
> > Best regards,
> > --
> > Justin Stitt <justinstitt@...gle.com>
> >