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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id a11-20020a170902eccb00b001bb28b9a40dsm9161300plh.11.2023.09.25.11.02.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Sep 2023 11:02:05 -0700 (PDT) Date: Mon, 25 Sep 2023 11:02:05 -0700 From: Kees Cook To: Justin Stitt Cc: Jean Delvare , Guenter Roeck , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v4] hwmon: (acpi_power_meter) replace open-coded kmemdup_nul Message-ID: <202309251101.1544F5F@keescook> References: <20230925-strncpy-drivers-hwmon-acpi_power_meter-c-v4-1-3bac7534f10f@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230925-strncpy-drivers-hwmon-acpi_power_meter-c-v4-1-3bac7534f10f@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 25, 2023 at 03:43:23AM +0000, Justin Stitt wrote: > `strncpy` is deprecated for use on NUL-terminated destination strings [1]. > > Let's refactor this kcalloc() + strncpy() into a kmemdup_nul() which has > more obvious behavior and is less error prone. > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt > --- > Changes in v4: > - drop +1 from length arg (thanks Kees) > - reword subject line (thanks Kees) > - rebase onto 6465e260f4879080 > - Link to v3: https://lore.kernel.org/r/20230921-strncpy-drivers-hwmon-acpi_power_meter-c-v3-1-307552c6ec3f@google.com > > Changes in v3: > - refactor to use kmemdup_nul() (thanks Thomas and Kees) > - change commit msg to reflect ^ > - rebase onto 2cf0f71562387282 > - Link to v2: https://lore.kernel.org/r/20230919-strncpy-drivers-hwmon-acpi_power_meter-c-v2-1-8348432d6442@google.com > > Changes in v2: > - use memcpy over strscpy (thanks Kees) > - Link to v1: https://lore.kernel.org/r/20230914-strncpy-drivers-hwmon-acpi_power_meter-c-v1-1-905297479fe8@google.com > --- > drivers/hwmon/acpi_power_meter.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c > index fa28d447f0df..c13b5c8a0433 100644 > --- a/drivers/hwmon/acpi_power_meter.c > +++ b/drivers/hwmon/acpi_power_meter.c > @@ -796,14 +796,13 @@ static int read_capabilities(struct acpi_power_meter_resource *resource) > goto error; > } > > - *str = kcalloc(element->string.length + 1, sizeof(u8), > - GFP_KERNEL); > + *str = kmemdup_nul(element->string.pointer, element->string.length, > + GFP_KERNEL); This whitespace looks weird -- I'd expect this to line up with "element", like this: > + *str = kmemdup_nul(element->string.pointer, element->string.length, > + GFP_KERNEL); Otherwise, yes, looks correct. -- Kees Cook