[PATCH V2 08/15] coresight: tmc: getting the right read_count on tmc_open()

Mathieu Poirier mathieu.poirier at linaro.org
Tue Apr 12 10:54:45 PDT 2016

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 at linaro.org>
 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 ae336641518f..4d7b64f69389 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__);

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