[PATCH AUTOSEL for 4.14 132/135] ath9k: fix tx99 potential info leak

[alexander . levin]

From: Miaoqing Pan <miaoqing@xxxxxxxxxxxxxx>

[ Upstream commit ee0a47186e2fa9aa1c56cadcea470ca0ba8c8692 ]

When the user sets count to zero the string buffer would remain
completely uninitialized which causes the kernel to parse its
own stack data, potentially leading to an info leak. In addition
to that, the string might be not terminated properly when the
user data does not contain a 0-terminator.

Signed-off-by: Miaoqing Pan <miaoqing@xxxxxxxxxxxxxx>
Reviewed-by: Christoph BÃhmwalder <christoph@xxxxxxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 drivers/net/wireless/ath/ath9k/tx99.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/tx99.c b/drivers/net/wireless/ath/ath9k/tx99.c
index 49ed1afb913c..fe3a8263b224 100644
--- a/drivers/net/wireless/ath/ath9k/tx99.c
+++ b/drivers/net/wireless/ath/ath9k/tx99.c
@@ -179,6 +179,9 @@ static ssize_t write_file_tx99(struct file *file, const char __user *user_buf,
 	ssize_t len;
 	int r;
 
+	if (count < 1)
+		return -EINVAL;
+
 	if (sc->cur_chan->nvifs > 1)
 		return -EOPNOTSUPP;
 
@@ -186,6 +189,8 @@ static ssize_t write_file_tx99(struct file *file, const char __user *user_buf,
 	if (copy_from_user(buf, user_buf, len))
 		return -EFAULT;
 
+	buf[len] = '\0';
+
 	if (strtobool(buf, &start))
 		return -EINVAL;
 
-- 
2.11.0