mailbox: mailbox-test: Prevent memory leak

If we set the Signal twice or more, without using it as part of a message,
memory will be re-allocated and the pointer over-written.  Prevent this
potential leak by only allocating memory when there isn't any already.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/mailbox/mailbox-test.c b/drivers/mailbox/mailbox-test.c
index 5f4b439fd45a..58d04726cdd7 100644
--- a/drivers/mailbox/mailbox-test.c
+++ b/drivers/mailbox/mailbox-test.c
@@ -59,9 +59,12 @@ static ssize_t mbox_test_signal_write(struct file *filp,
                 return -EINVAL;
         }
 
-        tdev->signal = kzalloc(MBOX_MAX_SIG_LEN, GFP_KERNEL);
-        if (!tdev->signal)
-                return -ENOMEM;
+        /* Only allocate memory if we need to */
+        if (!tdev->signal) {
+                tdev->signal = kzalloc(MBOX_MAX_SIG_LEN, GFP_KERNEL);
+                if (!tdev->signal)
+                        return -ENOMEM;
+        }
 
         if (copy_from_user(tdev->signal, userbuf, count)) {
                 kfree(tdev->signal);