coda: add error handling for fget

When fget fails, the lack of error-handling code may cause unexpected
results.

This patch adds error-handling code after calling fget.

Link: http://lkml.kernel.org/r/2514ec03df9c33b86e56748513267a80dd8004d9.1558117389.git.jaharkes@cs.cmu.eduSigned-off-by: Zhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Mikko Rapeli <mikko.rapeli@iki.fi>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/coda/psdev.c

@@ -182,8 +182,11 @@ static ssize_t coda_psdev_write(struct file *file, const char __user *buf,
 	if (req->uc_opcode == CODA_OPEN_BY_FD) {
 		struct coda_open_by_fd_out *outp =
 			(struct coda_open_by_fd_out *)req->uc_data;
-		if (!outp->oh.result)
+		if (!outp->oh.result) {
 			outp->fh = fget(outp->fd);
+			if (!outp->fh)
+				return -EBADF;
+		}
 	}
 
         wake_up(&req->uc_sleep);