libertas: potential oops in debugfs

If we do a zero size allocation then it will oops.  Also we can't be
sure the user passes us a NUL terminated string so I've added a
terminator.

This code can only be triggered by root.

Reported-by: Nico Golde <nico@ngolde.de>
Reported-by: Fabian Yamaguchi <fabs@goesec.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/net/wireless/libertas/debugfs.c b/drivers/net/wireless/libertas/debugfs.c
index 668dd27616a0..cc6a0a586f0b 100644
--- a/drivers/net/wireless/libertas/debugfs.c
+++ b/drivers/net/wireless/libertas/debugfs.c
@@ -913,7 +913,10 @@ static ssize_t lbs_debugfs_write(struct file *f, const char __user *buf,
         char *p2;
         struct debug_data *d = f->private_data;
 
-        pdata = kmalloc(cnt, GFP_KERNEL);
+        if (cnt == 0)
+                return 0;
+
+        pdata = kmalloc(cnt + 1, GFP_KERNEL);
         if (pdata == NULL)
                 return 0;
 
@@ -922,6 +925,7 @@ static ssize_t lbs_debugfs_write(struct file *f, const char __user *buf,
                 kfree(pdata);
                 return 0;
         }
+        pdata[cnt] = '\0';
 
         p0 = pdata;
         for (i = 0; i < num_of_items; i++) {