[PATCH AUTOSEL for 3.18 59/59] 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 2ea3589f709f..b7ab8455ffbd 100644
--- a/drivers/net/wireless/ath/ath9k/tx99.c
+++ b/drivers/net/wireless/ath/ath9k/tx99.c
@@ -180,6 +180,9 @@ 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;
 
@@ -187,6 +190,8 @@ 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