Commit 19bce474 authored by Hui Peng's avatar Hui Peng Committed by Takashi Iwai
Browse files

ALSA: usb-audio: Fix a stack buffer overflow bug in check_input_term 



`check_input_term` recursively calls itself with input from
device side (e.g., uac_input_terminal_descriptor.bCSourceID)
as argument (id). In `check_input_term`, if `check_input_term`
is called with the same `id` argument as the caller, it triggers
endless recursive call, resulting kernel space stack overflow.

This patch fixes the bug by adding a bitmap to `struct mixer_build`
to keep track of the checked ids and stop the execution if some id
has been checked (similar to how parse_audio_unit handles unitid
argument).

Reported-by: default avatarHui Peng <benquike@gmail.com>
Reported-by: default avatarMathias Payer <mathias.payer@nebelwelt.net>
Signed-off-by: default avatarHui Peng <benquike@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent daac0715

sound/usb/mixer.c

+27 −8
Original line number Diff line number Diff line
@@ -68,6 +68,7 @@ struct mixer_build { 
	unsigned char *buffer;

	unsigned int buflen;

	DECLARE_BITMAP(unitbitmap, MAX_ID_ELEMS);

	DECLARE_BITMAP(termbitmap, MAX_ID_ELEMS);

	struct usb_audio_term oterm;

	const struct usbmix_name_map *map;

	const struct usbmix_selector_map *selector_map;
@@ -775,16 +776,25 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, 
 * parse the source unit recursively until it reaches to a terminal

 * or a branched unit.

 */

static int check_input_term(struct mixer_build *state, int id,

static int __check_input_term(struct mixer_build *state, int id,

			    struct usb_audio_term *term)

{

	int protocol = state->mixer->protocol;

	int err;

	void *p1;

	unsigned char *hdr;



	memset(term, 0, sizeof(*term));

	while ((p1 = find_audio_control_unit(state, id)) != NULL) {

		unsigned char *hdr = p1;

	for (;;) {

		/* a loop in the terminal chain? */

		if (test_and_set_bit(id, state->termbitmap))

			return -EINVAL;



		p1 = find_audio_control_unit(state, id);

		if (!p1)

			break;



		hdr = p1;

		term->id = id;



		if (protocol == UAC_VERSION_1 || protocol == UAC_VERSION_2) {
@@ -802,7 +812,7 @@ static int check_input_term(struct mixer_build *state, int id, 


					/* call recursively to verify that the

					 * referenced clock entity is valid */

					err = check_input_term(state, d->bCSourceID, term);

					err = __check_input_term(state, d->bCSourceID, term);

					if (err < 0)

						return err;
@@ -836,7 +846,7 @@ static int check_input_term(struct mixer_build *state, int id, 
			case UAC2_CLOCK_SELECTOR: {

				struct uac_selector_unit_descriptor *d = p1;

				/* call recursively to retrieve the channel info */

				err = check_input_term(state, d->baSourceID[0], term);

				err = __check_input_term(state, d->baSourceID[0], term);

				if (err < 0)

					return err;

				term->type = UAC3_SELECTOR_UNIT << 16; /* virtual type */
@@ -899,7 +909,7 @@ static int check_input_term(struct mixer_build *state, int id, 


				/* call recursively to verify that the

				 * referenced clock entity is valid */

				err = check_input_term(state, d->bCSourceID, term);

				err = __check_input_term(state, d->bCSourceID, term);

				if (err < 0)

					return err;
@@ -950,7 +960,7 @@ static int check_input_term(struct mixer_build *state, int id, 
			case UAC3_CLOCK_SELECTOR: {

				struct uac_selector_unit_descriptor *d = p1;

				/* call recursively to retrieve the channel info */

				err = check_input_term(state, d->baSourceID[0], term);

				err = __check_input_term(state, d->baSourceID[0], term);

				if (err < 0)

					return err;

				term->type = UAC3_SELECTOR_UNIT << 16; /* virtual type */
@@ -966,7 +976,7 @@ static int check_input_term(struct mixer_build *state, int id, 
					return -EINVAL;



				/* call recursively to retrieve the channel info */

				err = check_input_term(state, d->baSourceID[0], term);

				err = __check_input_term(state, d->baSourceID[0], term);

				if (err < 0)

					return err;
@@ -984,6 +994,15 @@ static int check_input_term(struct mixer_build *state, int id, 
	return -ENODEV;

}





static int check_input_term(struct mixer_build *state, int id,

			    struct usb_audio_term *term)

{

	memset(term, 0, sizeof(*term));

	memset(state->termbitmap, 0, sizeof(state->termbitmap));

	return __check_input_term(state, id, term);

}



/*

 * Feature Unit

 */

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