[PATCH] megaraid: fix error code check of register_chrdev()

[Alexey Khoroshilov]

There is invalid error code check of register_chrdev() in megaraid_init().

register_chrdev() returns negative code in case of error,
as a result current code can try to unregister_chrdev() with error code
instead of major that may lead to unregistering somebody else's chardev.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshi...@ispras.ru>
---
 drivers/scsi/megaraid.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/megaraid.c b/drivers/scsi/megaraid.c
index 9d05302a3bcd..ded082942ca0 100644
--- a/drivers/scsi/megaraid.c
+++ b/drivers/scsi/megaraid.c
@@ -4702,7 +4702,7 @@ static int __init megaraid_init(void)
         * major number allocation.
         */
        major = register_chrdev(0, "megadev_legacy", &megadev_fops);
-       if (!major) {
+       if (major < 0) {
                printk(KERN_WARNING
                                "megaraid: failed to register char device\n");
        }
@@ -4715,7 +4715,10 @@ static void __exit megaraid_exit(void)
        /*
         * Unregister the character device interface to the driver.
         */
-       unregister_chrdev(major, "megadev_legacy");
+       if (major > 0) {
+               unregister_chrdev(major, "megadev_legacy");
+               major = 0;
+       }
 
        pci_unregister_driver(&megaraid_pci_driver);
 
-- 
1.9.1