ipmi:msghandler: Fix potential memory corruption in ipmi_create_user()

The "intf" list iterator is an invalid pointer if the correct
"intf->intf_num" is not found.  Calling atomic_dec(&intf->nr_users) on
and invalid pointer will lead to memory corruption.

We don't really need to call atomic_dec() if we haven't called
atomic_add_return() so update the if (intf->in_shutdown) path as well.

Fixes: 8e76741c3d8b ("ipmi: Add a limit on the number of users that may use IPMI")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Message-ID: <aBjMZ8RYrOt6NOgi@stanley.mountain>
Signed-off-by: Corey Minyard <corey@minyard.net>

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 8b2c3fca9c4cab9f09c44122409b7707c351faeb..064944ae9fdc39f8d866df2f1b23aba87627951d 100644 (file)
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -1240,12 +1240,12 @@ int ipmi_create_user(unsigned int          if_num,
        }
        /* Not found, return an error */
        rv = -EINVAL;
-       goto out_kfree;
+       goto out_unlock;
 
  found:
        if (intf->in_shutdown) {
                rv = -ENODEV;
-               goto out_kfree;
+               goto out_unlock;
        }
 
        if (atomic_add_return(1, &intf->nr_users) > max_users) {
@@ -1293,6 +1293,7 @@ out_kfree:
        } else {
                *user = new_user;
        }
+out_unlock:
        mutex_unlock(&ipmi_interfaces_mutex);
        return rv;
 }