[PATCH 0/2] Remove VLA usage in rtc-s5m

[PATCH 0/2] Remove VLA usage in rtc-s5m

[Gustavo A. R. Silva]

This patchset aims to remove VLA usage from rtc-s5m.

The first patch moves an enum from rtc.h to rtc-s5m.c, as this is the
only driver in which such enum is actually being used [1].

The second patch adds the enum name RTC_MAX_NUM_TIME_REGS, which will
be used as a maximum length to the current VLAs, hence turning them
into fixed-length arrays instead.

[1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2

Thanks

Gustavo A. R. Silva (2):
  rtc: s5m: move enum from rtc.h to rtc-s5m.c
  rtc: s5m: Remove VLA usage

 drivers/rtc/rtc-s5m.c           | 25 +++++++++++++++++++------
 include/linux/mfd/samsung/rtc.h | 11 -----------
 2 files changed, 19 insertions(+), 17 deletions(-)

-- 
2.7.4

[PATCH 1/2] rtc: s5m: Move enum from rtc.h to rtc-s5m.c

[Gustavo A. R. Silva]

Move this enum to rtc-s5m.c once it is meaningless to others drivers [1].

[1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/rtc/rtc-s5m.c           | 11 +++++++++++
 include/linux/mfd/samsung/rtc.h | 11 -----------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/rtc/rtc-s5m.c b/drivers/rtc/rtc-s5m.c
index 6deae10..4c363de 100644
--- a/drivers/rtc/rtc-s5m.c
+++ b/drivers/rtc/rtc-s5m.c
@@ -38,6 +38,17 @@
  */
 #define UDR_READ_RETRY_CNT	5
 
+enum {
+	RTC_SEC = 0,
+	RTC_MIN,
+	RTC_HOUR,
+	RTC_WEEKDAY,
+	RTC_DATE,
+	RTC_MONTH,
+	RTC_YEAR1,
+	RTC_YEAR2,
+};
+
 /*
  * Registers used by the driver which are different between chipsets.
  *
diff --git a/include/linux/mfd/samsung/rtc.h b/include/linux/mfd/samsung/rtc.h
index 48c3c5b..9ed2871 100644
--- a/include/linux/mfd/samsung/rtc.h
+++ b/include/linux/mfd/samsung/rtc.h
@@ -141,15 +141,4 @@ enum s2mps_rtc_reg {
 #define WTSR_ENABLE_SHIFT	6
 #define WTSR_ENABLE_MASK	(1 << WTSR_ENABLE_SHIFT)
 
-enum {
-	RTC_SEC = 0,
-	RTC_MIN,
-	RTC_HOUR,
-	RTC_WEEKDAY,
-	RTC_DATE,
-	RTC_MONTH,
-	RTC_YEAR1,
-	RTC_YEAR2,
-};
-
 #endif /*  __LINUX_MFD_SEC_RTC_H */
-- 
2.7.4

[PATCH 2/2] rtc: s5m: Remove VLA usage

[Gustavo A. R. Silva]

In preparation to enabling -Wvla, remove VLAs and replace them
with fixed-length arrays instead.

>From a security viewpoint, the use of Variable Length Arrays can be
a vector for stack overflow attacks. Also, in general, as the code
evolves it is easy to lose track of how big a VLA can get. Thus, we
can end up having segfaults that are hard to debug.

Also, fixed as part of the directive to remove all VLAs from
the kernel: https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/rtc/rtc-s5m.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-s5m.c b/drivers/rtc/rtc-s5m.c
index 4c363de..8428455 100644
--- a/drivers/rtc/rtc-s5m.c
+++ b/drivers/rtc/rtc-s5m.c
@@ -47,6 +47,8 @@ enum {
 	RTC_MONTH,
 	RTC_YEAR1,
 	RTC_YEAR2,
+	/* Make sure this is always the last enum name. */
+	RTC_MAX_NUM_TIME_REGS
 };
 
 /*
@@ -378,7 +380,7 @@ static void s5m8763_tm_to_data(struct rtc_time *tm, u8 *data)
 static int s5m_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
-	u8 data[info->regs->regs_count];
+	u8 data[RTC_MAX_NUM_TIME_REGS];
 	int ret;
 
 	if (info->regs->read_time_udr_mask) {
@@ -424,7 +426,7 @@ static int s5m_rtc_read_time(struct device *dev, struct rtc_time *tm)
 static int s5m_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
-	u8 data[info->regs->regs_count];
+	u8 data[RTC_MAX_NUM_TIME_REGS];
 	int ret = 0;
 
 	switch (info->device_type) {
@@ -461,7 +463,7 @@ static int s5m_rtc_set_time(struct device *dev, struct rtc_time *tm)
 static int s5m_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
-	u8 data[info->regs->regs_count];
+	u8 data[RTC_MAX_NUM_TIME_REGS];
 	unsigned int val;
 	int ret, i;
 
@@ -511,7 +513,7 @@ static int s5m_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 
 static int s5m_rtc_stop_alarm(struct s5m_rtc_info *info)
 {
-	u8 data[info->regs->regs_count];
+	u8 data[RTC_MAX_NUM_TIME_REGS];
 	int ret, i;
 	struct rtc_time tm;
 
@@ -556,7 +558,7 @@ static int s5m_rtc_stop_alarm(struct s5m_rtc_info *info)
 static int s5m_rtc_start_alarm(struct s5m_rtc_info *info)
 {
 	int ret;
-	u8 data[info->regs->regs_count];
+	u8 data[RTC_MAX_NUM_TIME_REGS];
 	u8 alarm0_conf;
 	struct rtc_time tm;
 
@@ -609,7 +611,7 @@ static int s5m_rtc_start_alarm(struct s5m_rtc_info *info)
 static int s5m_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
-	u8 data[info->regs->regs_count];
+	u8 data[RTC_MAX_NUM_TIME_REGS];
 	int ret;
 
 	switch (info->device_type) {
-- 
2.7.4

Re: [PATCH 1/2] rtc: s5m: Move enum from rtc.h to rtc-s5m.c

[Krzysztof Kozlowski]

On Sat, Mar 10, 2018 at 7:27 AM, Gustavo A. R. Silva
<gustavo@embeddedor.com> wrote:
> Move this enum to rtc-s5m.c once it is meaningless to others drivers [1].
>
> [1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2

Instead of external link (which might or might not work soon) you can
just put "Suggested-by: Krzysztof Kozlowski <krzk@kernel.org>".

Anyway:
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof

Re: [PATCH 1/2] rtc: s5m: Move enum from rtc.h to rtc-s5m.c

[Lee Jones]

On Sat, 10 Mar 2018, Gustavo A. R. Silva wrote:

> Move this enum to rtc-s5m.c once it is meaningless to others drivers [1].
> 
> [1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/rtc/rtc-s5m.c           | 11 +++++++++++
>  include/linux/mfd/samsung/rtc.h | 11 -----------

I don't think this will conflict with anything (unless some major
works are carried out within the next few weeks - in which case I'll
need a pull-request, but for now ...)

Acked-by: Lee Jones <lee.jones@linaro.org>

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH 2/2] rtc: s5m: Remove VLA usage

[Krzysztof Kozlowski]

On Sat, Mar 10, 2018 at 7:27 AM, Gustavo A. R. Silva
<gustavo@embeddedor.com> wrote:
> In preparation to enabling -Wvla, remove VLAs and replace them
> with fixed-length arrays instead.
>
> From a security viewpoint, the use of Variable Length Arrays can be
> a vector for stack overflow attacks. Also, in general, as the code
> evolves it is easy to lose track of how big a VLA can get. Thus, we
> can end up having segfaults that are hard to debug.
>
> Also, fixed as part of the directive to remove all VLAs from
> the kernel: https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/rtc/rtc-s5m.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)


Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof

Re: [PATCH 0/2] Remove VLA usage in rtc-s5m

[Alexandre Belloni]

Hi,

On 10/03/2018 at 00:27:02 -0600, Gustavo A. R. Silva wrote:
> This patchset aims to remove VLA usage from rtc-s5m.
> 
> The first patch moves an enum from rtc.h to rtc-s5m.c, as this is the
> only driver in which such enum is actually being used [1].
> 
> The second patch adds the enum name RTC_MAX_NUM_TIME_REGS, which will
> be used as a maximum length to the current VLAs, hence turning them
> into fixed-length arrays instead.
> 
> [1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2
> 
> Thanks
> 
> Gustavo A. R. Silva (2):
>   rtc: s5m: move enum from rtc.h to rtc-s5m.c
>   rtc: s5m: Remove VLA usage
> 

Both applied, thanks.

-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH 0/2] Remove VLA usage in rtc-s5m

[Gustavo A. R. Silva]

On 03/12/2018 07:35 PM, Alexandre Belloni wrote:
> Hi,
> 
> On 10/03/2018 at 00:27:02 -0600, Gustavo A. R. Silva wrote:
>> This patchset aims to remove VLA usage from rtc-s5m.
>>
>> The first patch moves an enum from rtc.h to rtc-s5m.c, as this is the
>> only driver in which such enum is actually being used [1].
>>
>> The second patch adds the enum name RTC_MAX_NUM_TIME_REGS, which will
>> be used as a maximum length to the current VLAs, hence turning them
>> into fixed-length arrays instead.
>>
>> [1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2
>>
>> Thanks
>>
>> Gustavo A. R. Silva (2):
>>    rtc: s5m: move enum from rtc.h to rtc-s5m.c
>>    rtc: s5m: Remove VLA usage
>>
> 
> Both applied, thanks.
> 

Awesome.

Thank you.
--
Gustavo

Re: [PATCH 1/2] rtc: s5m: Move enum from rtc.h to rtc-s5m.c

[Gustavo A. R. Silva]

On 03/11/2018 11:39 AM, Krzysztof Kozlowski wrote:
> On Sat, Mar 10, 2018 at 7:27 AM, Gustavo A. R. Silva
> <gustavo@embeddedor.com> wrote:
>> Move this enum to rtc-s5m.c once it is meaningless to others drivers [1].
>>
>> [1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2
> 
> Instead of external link (which might or might not work soon) you can
> just put "Suggested-by: Krzysztof Kozlowski <krzk@kernel.org>".
> 

I got it.
I'll do that next time.

> Anyway:
> Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
> 

Thanks for reviewing it.
--
Gustavo