[PATCH v4 3/6] iio: fix potential out-of-bound write

[Markus Burri]

The buffer is set to 20 characters. If a caller write more characters,
count is truncated to the max available space in "simple_write_to_buffer".
To protect from OoB access, check that the input size fit into buffer and
add a zero terminator after copy to the end of the copied data.

Signed-off-by: Markus Burri <markus.burri at mt.com>
---
 drivers/iio/industrialio-core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index b9f4113ae5fc..ebf17ea5a5f9 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -410,12 +410,15 @@ static ssize_t iio_debugfs_write_reg(struct file *file,
 	char buf[80];
 	int ret;
 
+	if (count >= sizeof(buf))
+		return -EINVAL;
+
 	ret = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf,
 				     count);
 	if (ret < 0)
 		return ret;
 
-	buf[count] = '\0';
+	buf[ret] = '\0';
 
 	ret = sscanf(buf, "%i %i", &reg, &val);
 
-- 
2.39.5