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Commit 2bac3a35 authored by Hui Peng's avatar Hui Peng Committed by Greg Kroah-Hartman
Browse files

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



commit 19bce474c45be69a284ecee660aa12d8f1e88f18 upstream.

`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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 669a5055

sound/usb/mixer.c

+24 −5
Original line number Diff line number Diff line
@@ -82,6 +82,7 @@ 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;
@@ -710,15 +711,24 @@ static int get_term_name(struct mixer_build *state, struct usb_audio_term *iterm 
 * 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 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;

		switch (hdr[2]) {

		case UAC_INPUT_TERMINAL:
@@ -733,7 +743,7 @@ 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;
@@ -765,7 +775,7 @@ 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 = d->bDescriptorSubtype << 16; /* virtual type */
@@ -812,6 +822,15 @@ 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

 */