drivers/char/hvc_console.c: adjust call to put_tty_driver

The call to put_tty_driver is out of place and is applied to the wrong
argument.

The function enclosing the patched code calls alloc_tty_driver and stores
the result in drv.  Subsequently, there are two occurrences of error
handling code, one making a goto to put_tty and one making a goto to
stop_thread.  At the point of the first one the assignment hvc_driver = drv
has not yet been executed, and from inspecting the rest of the file it
seems that hvc_driver would be NULL.  Thus the current call to
put_tty_driver is useless, and one applied to drv is needed.  The goto
stop_thread is in the error handling code for a call to
tty_register_driver, but the error cases in tty_register_driver do not free
its argument, so it should be done here.  Thus, I have moved the put_tty
label after the stop_thread label, so that put_tty_driver is called in both
cases.

The semantic match that finds this problem is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@r exists@
local idexpression x;
expression E,f;
position p1,p2,p3;
identifier l;
statement S;
@@

x = alloc_tty_driver@p1(...)
...
if (x == NULL) S
... when != E = x
    when != put_tty_driver(x)
goto@p2 l;
... when != E = x
    when != f(...,x,...)
    when any
(
return \(0\|x\);
|
return@p3 ...;
)

@script:python@
p1 << r.p1;
p2 << r.p2;
p3 << r.p3;
@@

print "%s: call on line %s not freed or saved before return on line %s via line %s" % (p1[0].file,p1[0].line,p3[0].line,p2[0].line)
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/hvc_console.c

@@ -819,11 +819,11 @@ static int hvc_init(void)
 	hvc_driver = drv;
 	return 0;
 
-put_tty:
-	put_tty_driver(hvc_driver);
 stop_thread:
 	kthread_stop(hvc_task);
 	hvc_task = NULL;
+put_tty:
+	put_tty_driver(drv);
 out:
 	return err;
 }