[PATCH V3 10/18] coresight: tmc: getting the right read_count on tmc_open()

From: Mathieu Poirier
Date: Fri Apr 22 2016 - 13:16:43 EST

In function tmc_open(), if tmc_read_prepare() fails variable
drvdata->read_count is not decremented, causing unwanted
access to drvdata->buf and very likely, a crash dump.

By moving the incrementation to a place where we know things
are stable this kind of situation is avoided.

Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Reviewed-by: Suzuki K Poulose <Suzuki.Poulose@xxxxxxx>
drivers/hwtracing/coresight/coresight-tmc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
index e8e12a9b917a..55806352b1f1 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -121,13 +121,14 @@ static int tmc_open(struct inode *inode, struct file *file)
struct tmc_drvdata, miscdev);
int ret = 0;

- if (drvdata->read_count++)
+ if (drvdata->read_count)
goto out;

ret = tmc_read_prepare(drvdata);
if (ret)
return ret;
+ drvdata->read_count++;
nonseekable_open(inode, file);

dev_dbg(drvdata->dev, "%s: successfully opened\n", __func__);