tty_register_driver: only allocate tty instances when defined

If device->num is zero we attempt to kmalloc() zero bytes.  When SLUB is
enabled this returns a null pointer and take that as an allocation failure
and fail the device register.  Check for no devices and avoid the
allocation.

[akpm: opportunistic kzalloc() conversion]
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 7a32df59490750775b6df3b718e0b33be2ee8514..389da364e6b6ebb2a70e732927e3e6e92f01243e 100644 (file)
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -3720,11 +3720,10 @@ int tty_register_driver(struct tty_driver *driver)
        if (driver->flags & TTY_DRIVER_INSTALLED)
                return 0;
 
-       if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
-               p = kmalloc(driver->num * 3 * sizeof(void *), GFP_KERNEL);
+       if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM) && driver->num) {
+               p = kzalloc(driver->num * 3 * sizeof(void *), GFP_KERNEL);
                if (!p)
                        return -ENOMEM;
-               memset(p, 0, driver->num * 3 * sizeof(void *));
        }
 
        if (!driver->major) {