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Subject[PATCH 2/2] 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>
---
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
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