On 9/1/19 9:00 AM, Salvatore Bonaccorso wrote:
> Hi Hui,
>
> On Fri, Aug 30, 2019 at 05:47:29PM -0400, Hui Peng wrote:
>> `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).
>>
>> CVE: CVE-2018-15118
> Similar to the previous one, this should be CVE-2019-15118 as far I
> can tell.
Same here: CVE id updated.
Can you apply it to v4.4.190 and v4.14.141?
Thanks.
>
> Regards,
> Salvatore
>From f5e478c4807b16f49c00316fb80485562b84340a Mon Sep 17 00:00:00 2001
From: Hui Peng <benquike@xxxxxxxxx>
Date: Fri, 30 Aug 2019 16:20:41 -0400
Subject: [PATCH 2/2] 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).
CVE: CVE-2019-15118
Reported-by: Hui Peng <benquike@xxxxxxxxx>
Reported-by: Mathias Payer <mathias.payer@xxxxxxxxxxxxx>
Signed-off-by: Hui Peng <benquike@xxxxxxxxx>
---
sound/usb/mixer.c | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 10ddec76f906..e24572fd6e30 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -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;
@@ -709,15 +710,24 @@ 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:
@@ -732,7 +742,7 @@ 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;
@@ -764,7 +774,7 @@ 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 */
@@ -811,6 +821,15 @@ 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
*/
--
2.17.1
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