firmware: fix __getname() missing failure check

The request_firmware*() APIs uses __getname() to iterate
over the list of paths possible for firmware to be found,
the code however never checked for failure on __getname().
Although *very unlikely*, this can still happen. Add the
missing check.

There is still no checks on the concatenation of the path
and filename passed, that requires a bit more work and
subsequent patches address this. The commit that introduced
this is abb139e7 ("firmware: teach the kernel to load
firmware files directly from the filesystem").

mcgrof@ergon ~/linux (git::firmware-fixes) $ git describe --contains abb139e7
v3.7-rc1~120

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: David Howells <dhowells@redhat.com>
Cc: Kyle McMartin <kyle@kernel.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/firmware_class.c

@@ -322,7 +322,11 @@ static int fw_get_filesystem_firmware(struct device *device,
 {
 	int i;
 	int rc = -ENOENT;
-	char *path = __getname();
+	char *path;
+
+	path = __getname();
+	if (!path)
+		return -ENOMEM;
 
 	for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
 		struct file *file;