Commit message: ALSA: usb-audio: Fix gpf in snd_usb_pipe_sanity_check

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>
CVE: CVE-2019-15222
CWE: CWE-476
Vulnerability description: An issue was discovered in the Linux kernel before 5.2.8. There is a NULL pointer dereference caused by a malicious USB device in the sound/usb/helper.c (motu_microbookii) driver.

Project: linux
File: helper.c

void *snd_usb_find_csint_desc(void *buffer, int buflen, void *after, u8 dsubtype)
{
	unsigned char *p = after;

	while ((p = snd_usb_find_desc(buffer, buflen, p,
				      USB_DT_CS_INTERFACE)) != NULL) {
		if (p[0] >= 3 && p[2] == dsubtype)
			return p;
	}
	return NULL;
}

Project: linux
File: helper.c

void *snd_usb_find_desc(void *descstart, int desclen, void *after, u8 dtype)
{
	u8 *p, *end, *next;

	p = descstart;
	end = p + desclen;
	for (; p < end;) {
		if (p[0] < 2)
			return NULL;
		next = p + p[0];
		if (next > end)
			return NULL;
		if (p[1] == dtype && (!after || (void *)p > after)) {
			return p;
		}
		p = next;
	}
	return NULL;
}

Project: linux
File: helper.c

unsigned char snd_usb_parse_datainterval(struct snd_usb_audio *chip,
					 struct usb_host_interface *alts)
{
	switch (snd_usb_get_speed(chip->dev)) {
	case USB_SPEED_HIGH:
	case USB_SPEED_WIRELESS:
	case USB_SPEED_SUPER:
	case USB_SPEED_SUPER_PLUS:
		if (get_endpoint(alts, 0)->bInterval >= 1 &&
		    get_endpoint(alts, 0)->bInterval <= 4)
			return get_endpoint(alts, 0)->bInterval - 1;
		break;
	default:
		break;
	}
	return 0;
}

Project: linux
File: helper.c

unsigned int snd_usb_combine_bytes(unsigned char *bytes, int size)
{
	switch (size) {
	case 1:  return *bytes;
	case 2:  return combine_word(bytes);
	case 3:  return combine_triple(bytes);
	case 4:  return combine_quad(bytes);
	default: return 0;
	}
}

Project: linux
File: helper.c

int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe, __u8 request,
		    __u8 requesttype, __u16 value, __u16 index, void *data,
		    __u16 size)
{
	int err;
	void *buf = NULL;
	int timeout;

	if (snd_usb_pipe_sanity_check(dev, pipe))
		return -EINVAL;

	if (size > 0) {
		buf = kmemdup(data, size, GFP_KERNEL);
		if (!buf)
			return -ENOMEM;
	}

	if (requesttype & USB_DIR_IN)
		timeout = USB_CTRL_GET_TIMEOUT;
	else
		timeout = USB_CTRL_SET_TIMEOUT;

	err = usb_control_msg(dev, pipe, request, requesttype,
			      value, index, buf, size, timeout);

	if (size > 0) {
		memcpy(data, buf, size);
		kfree(buf);
	}

	snd_usb_ctl_msg_quirk(dev, pipe, request, requesttype,
			      value, index, data, size);

	return err;
}

Project: linux
File: helper.c

int snd_usb_pipe_sanity_check(struct usb_device *dev, unsigned int pipe)
{
	static const int pipetypes[4] = {
		PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT
	};
	struct usb_host_endpoint *ep;

	ep = usb_pipe_endpoint(dev, pipe);
	if (!ep || usb_pipetype(pipe) != pipetypes[usb_endpoint_type(&ep->desc)])
		return -EINVAL;
	return 0;
}