ALSA: usb-audio: Fix gpf in snd_usb_pipe_sanity_check

[ Upstream commit 5d78e1c2b7f4be00bbe62141603a631dc7812f35 ]

syzbot found the following crash on:

  general protection fault: 0000 [#1] SMP KASAN
  RIP: 0010:snd_usb_pipe_sanity_check+0x80/0x130 sound/usb/helper.c:75
  Call Trace:
    snd_usb_motu_microbookii_communicate.constprop.0+0xa0/0x2fb  sound/usb/quirks.c:1007
    snd_usb_motu_microbookii_boot_quirk sound/usb/quirks.c:1051 [inline]
    snd_usb_apply_boot_quirk.cold+0x163/0x370 sound/usb/quirks.c:1280
    usb_audio_probe+0x2ec/0x2010 sound/usb/card.c:576
    usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
    really_probe+0x281/0x650 drivers/base/dd.c:548
    ....

It was introduced in commit 801ebf1043ae for checking pipe and endpoint
types. It is fixed by adding a check of the ep pointer in question.

BugLink: https://syzkaller.appspot.com/bug?extid=d59c4387bfb6eced94e2


Reported-by: syzbot <syzbot+d59c4387bfb6eced94e2@syzkaller.appspotmail.com>
Fixes: 801ebf1043ae ("ALSA: usb-audio: Sanity checks for each pipe and EP types")
Cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 5c4b0a778419d9deab8557265f4b3fd6f0e97e11)
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>