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Message-ID: <a2bdac6a8914a76ed122438547f3697611299c0f.camel@linux.intel.com>
Subject: Re: [PATCH] thermal: intel: int340x_thermal: replace deprecated
 strncpy with strscpy
From: srinivas pandruvada <srinivas.pandruvada@linux.intel.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>, Justin Stitt
	 <justinstitt@google.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>, Zhang Rui
 <rui.zhang@intel.com>,  Lukasz Luba <lukasz.luba@arm.com>,
 linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, 
 linux-hardening@vger.kernel.org
Date: Tue, 19 Mar 2024 09:20:26 -0700
In-Reply-To: <CAJZ5v0j=cYbqyfi6y45hnu+Y_tvMGYb9p6d=kpsOA0AsxBoy3g@mail.gmail.com>
References: 
	<20240318-strncpy-drivers-thermal-intel-int340x_thermal-acpi_thermal_rel-c-v1-1-08839fbf737a@google.com>
	 <CAJZ5v0j=cYbqyfi6y45hnu+Y_tvMGYb9p6d=kpsOA0AsxBoy3g@mail.gmail.com>
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On Tue, 2024-03-19 at 12:39 +0100, Rafael J. Wysocki wrote:
> On Mon, Mar 18, 2024 at 11:36=E2=80=AFPM Justin Stitt
> <justinstitt@google.com> wrote:
> >=20
> > strncpy() is deprecated for use on NUL-terminated destination
> > strings
> > [1] and as such we should prefer more robust and less ambiguous
> > string
> > interfaces.
> >=20
> > psvt->limit.string can only be 8 bytes so let's use the appropriate
> > size
> > macro ACPI_LIMIT_STR_MAX_LEN.
> >=20
> > 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.
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 memset(&psvt->limit, 0, sizeof(u64));
> > and
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 psvt_user =3D kzalloc(psvt_len, GFP_KE=
RNEL);
> >=20
> > Let's use `strscpy` [2] due to the fact that it guarantees
> > NUL-termination on the destination buffer without unnecessarily
> > NUL-padding.
> >=20
> > Link:
> > https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-=
on-nul-terminated-strings
> > =C2=A0[1]
> > Link:
> > https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
> > =C2=A0[2]
> > Link: https://github.com/KSPP/linux/issues/90
> > Cc: linux-hardening@vger.kernel.org
> > Signed-off-by: Justin Stitt <justinstitt@google.com>
>=20
> Srinivas, any objections?
No

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

>=20
> > ---
> > Note: build-tested only.
> >=20
> > Found with: $ rg "strncpy\("
> > ---
> > =C2=A0drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c | 4 ++--
> > =C2=A01 file changed, 2 insertions(+), 2 deletions(-)
> >=20
> > 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
> >=20
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 if (knob->type =3D=3D ACPI_TYPE_STRING) {
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 memse=
t(&psvt->limit, 0, sizeof(u64));
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 strncpy(psv=
t->limit.string, psvt_ptr-
> > >limit.str_ptr, knob->string.length);
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 strscpy(psv=
t->limit.string, psvt_ptr-
> > >limit.str_ptr, ACPI_LIMIT_STR_MAX_LEN);
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 } else {
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 psvt-=
>limit.integer =3D psvt_ptr-
> > >limit.integer;
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 }
> > @@ -468,7 +468,7 @@ static int fill_psvt(char __user *ubuf)
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 psvt_user[i].unlimit_coeff =3D
> > psvts[i].unlimit_coeff;
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 psvt_user[i].control_knob_type =3D
> > psvts[i].control_knob_type;
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 if (psvt_user[i].control_knob_type =3D=3D
> > ACPI_TYPE_STRING)
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 strncpy(psv=
t_user[i].limit.string,
> > psvts[i].limit.string,
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 strscpy(psv=
t_user[i].limit.string,
> > psvts[i].limit.string,
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ACPI_LIMIT_STR_MAX_LEN);
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 else
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 psvt_=
user[i].limit.integer =3D
> > psvts[i].limit.integer;
> >=20
> > ---
> > base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400
> > change-id: 20240318-strncpy-drivers-thermal-intel-int340x_thermal-
> > acpi_thermal_rel-c-17070c1e42f3
> >=20
> > Best regards,
> > --
> > Justin Stitt <justinstitt@google.com>
> >=20