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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: Hui Peng <benquike@gmail.com>
Reported-by: Mathias Payer <mathias.payer@nebelwelt.net>
Signed-off-by: Hui Peng <benquike@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Hui Peng 2019-08-15 00:31:34 -04:00 committed by Takashi Iwai
parent daac07156b
commit 19bce474c4
1 changed files with 27 additions and 8 deletions
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35
sound/usb/mixer.c
View File

@ -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
*/