net/mlx5: Fix incorrect raw command length parsing

BugLink: https://bugs.launchpad.net/bugs/1790884

[ Upstream commit 603b7bcf ]

The NULL character was not set correctly for the string containing
the command length, this caused failures reading the output of the
command due to a random length. The fix is to initialize the output
length string.

Fixes: e126ba97 ("mlx5: Add driver for Mellanox Connect-IB adapters")
Signed-off-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/ethernet/mellanox/mlx5/core/cmd.c

@@ -1126,7 +1126,7 @@ static ssize_t outlen_write(struct file *filp, const char __user *buf,
 {
 	struct mlx5_core_dev *dev = filp->private_data;
 	struct mlx5_cmd_debug *dbg = &dev->cmd.dbg;
-	char outlen_str[8];
+	char outlen_str[8] = {0};
 	int outlen;
 	void *ptr;
 	int err;
@@ -1141,8 +1141,6 @@ static ssize_t outlen_write(struct file *filp, const char __user *buf,
 	if (copy_from_user(outlen_str, buf, count))
 		return -EFAULT;
 
-	outlen_str[7] = 0;
-
 	err = sscanf(outlen_str, "%d", &outlen);
 	if (err < 0)
 		return err;