rtc: s5m: Remove VLA usage

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>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/rtc/rtc-s5m.c b/drivers/rtc/rtc-s5m.c
index 4c363deb79fd..8428455432ca 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) {