ALSA: usx2y: Don't call free_pages_exact() with NULL address

[ Upstream commit cae0cf651adccee2c3f376e78f30fbd788d0829f ]

Unlike some other functions, we can't pass NULL pointer to
free_pages_exact().  Add a proper NULL check for avoiding possible
Oops.

Link: https://lore.kernel.org/r/20210517131545.27252-10-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/sound/usb/usx2y/usb_stream.c b/sound/usb/usx2y/usb_stream.c
index 091c071b270af30925223b9ede5813e23fc82099..cff684942c4f0ff22c43cff9cc7b7d346e5c7bc2 100644 (file)
--- a/sound/usb/usx2y/usb_stream.c
+++ b/sound/usb/usx2y/usb_stream.c
@@ -142,8 +142,11 @@ void usb_stream_free(struct usb_stream_kernel *sk)
        if (!s)
                return;
 
-       free_pages_exact(sk->write_page, s->write_size);
-       sk->write_page = NULL;
+       if (sk->write_page) {
+               free_pages_exact(sk->write_page, s->write_size);
+               sk->write_page = NULL;
+       }
+
        free_pages_exact(s, s->read_size);
        sk->s = NULL;
 }