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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).

Change-Id: Ibc4ab23c7d7c2fc96ff85d7cf1a1205bbd632cb5
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 L R
parent 8290b69077
commit e49b967f0b
1 changed files with 24 additions and 5 deletions
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29
sound/usb/mixer.c
View File

@ -81,6 +81,7 @@ 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;
@ -671,14 +672,24 @@ 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, struct usb_audio_term *term)
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:
@ -696,7 +707,7 @@ static int check_input_term(struct mixer_build *state, int id, struct usb_audio_
term->name = d->iTerminal;
/* call recursively to get the clock selectors */
err = check_input_term(state, d->bCSourceID, term);
err = __check_input_term(state, d->bCSourceID, term);
if (err < 0)
return err;
}
@ -719,7 +730,7 @@ static int check_input_term(struct mixer_build *state, int id, struct usb_audio_
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 */
@ -767,6 +778,14 @@ static int check_input_term(struct mixer_build *state, int id, struct usb_audio_
}
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
*/