[alsa-devel] [PATCH] Fix an OOB bug in parse_audio_mixer_unit
The `uac_mixer_unit_descriptor` shown as below is read from the device side. In `parse_audio_mixer_unit`, `baSourceID` field is accessed from index 0 to `bNrInPins` - 1, the current implementation assumes that descriptor is always valid (the length of descriptor is no shorter than 5 + `bNrInPins`). If a descriptor read from the device side is invalid, it may trigger out-of-bound memory access.
``` struct uac_mixer_unit_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bDescriptorSubtype; __u8 bUnitID; __u8 bNrInPins; __u8 baSourceID[]; } ```
This patch fixes the bug by add a sanity check on the length of the descriptor.
Signed-off-by: Hui Peng benquike@gmail.com Reported-by: Hui Peng benquike@gmail.com Reported-by: Mathias Payer mathias.payer@nebelwelt.net --- sound/usb/mixer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 7498b5191b68..38202ce67237 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, struct usb_audio_term iterm; int input_pins, num_ins, num_outs; int pin, ich, err; + int desc_len = (int) ((unsigned long) state->buffer + + state->buflen - (unsigned long) raw_desc); + + if (desc_len < sizeof(*desc) + desc->bNrInPins) { + usb_audio_err(state->chip, + "descriptor %d too short\n", + unitid); + return -EINVAL; + }
err = uac_mixer_unit_get_channels(state, desc); if (err < 0) {
The attached file is the KASAN report.
On Tue, Aug 13, 2019 at 10:37 PM Hui Peng benquike@gmail.com wrote:
The `uac_mixer_unit_descriptor` shown as below is read from the device side. In `parse_audio_mixer_unit`, `baSourceID` field is accessed from index 0 to `bNrInPins` - 1, the current implementation assumes that descriptor is always valid (the length of descriptor is no shorter than 5 + `bNrInPins`). If a descriptor read from the device side is invalid, it may trigger out-of-bound memory access.
struct uac_mixer_unit_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bDescriptorSubtype; __u8 bUnitID; __u8 bNrInPins; __u8 baSourceID[]; }This patch fixes the bug by add a sanity check on the length of the descriptor.
Signed-off-by: Hui Peng benquike@gmail.com Reported-by: Hui Peng benquike@gmail.com Reported-by: Mathias Payer mathias.payer@nebelwelt.net
sound/usb/mixer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 7498b5191b68..38202ce67237 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, struct usb_audio_term iterm; int input_pins, num_ins, num_outs; int pin, ich, err;
int desc_len = (int) ((unsigned long) state->buffer +state->buflen - (unsigned long) raw_desc);if (desc_len < sizeof(*desc) + desc->bNrInPins) {usb_audio_err(state->chip,"descriptor %d too short\n",unitid);return -EINVAL;} err = uac_mixer_unit_get_channels(state, desc); if (err < 0) {-- 2.22.1
On Wed, 14 Aug 2019 04:36:24 +0200, Hui Peng wrote:
The `uac_mixer_unit_descriptor` shown as below is read from the device side. In `parse_audio_mixer_unit`, `baSourceID` field is accessed from index 0 to `bNrInPins` - 1, the current implementation assumes that descriptor is always valid (the length of descriptor is no shorter than 5 + `bNrInPins`). If a descriptor read from the device side is invalid, it may trigger out-of-bound memory access.
struct uac_mixer_unit_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bDescriptorSubtype; __u8 bUnitID; __u8 bNrInPins; __u8 baSourceID[]; }This patch fixes the bug by add a sanity check on the length of the descriptor.
Signed-off-by: Hui Peng benquike@gmail.com Reported-by: Hui Peng benquike@gmail.com Reported-by: Mathias Payer mathias.payer@nebelwelt.net
sound/usb/mixer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 7498b5191b68..38202ce67237 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, struct usb_audio_term iterm; int input_pins, num_ins, num_outs; int pin, ich, err;
int desc_len = (int) ((unsigned long) state->buffer +
state->buflen - (unsigned long) raw_desc);if (desc_len < sizeof(*desc) + desc->bNrInPins) {
usb_audio_err(state->chip,"descriptor %d too short\n",unitid);return -EINVAL;}
err = uac_mixer_unit_get_channels(state, desc); if (err < 0) {
Hm, what is the desc->bLength value in the error case?
Basically the buffer boundary is already checked against bLength in snd_usb_find_desc() which is called from obtaining the raw_desc in the caller of this function (parse_audio_unit()).
So, if any, we need to check bLength for the possible overflow like below.
thanks,
Takashi
--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -744,6 +744,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, return -EINVAL; if (!desc->bNrInPins) return -EINVAL; + if (desc->bLength < sizeof(*desc) + desc->bNrInPins) + return -EINVAL;
switch (state->mixer->protocol) { case UAC_VERSION_1:
On Wed, Aug 14, 2019 at 08:36:42AM +0200, Takashi Iwai wrote:
On Wed, 14 Aug 2019 04:36:24 +0200, Hui Peng wrote:
The `uac_mixer_unit_descriptor` shown as below is read from the device side. In `parse_audio_mixer_unit`, `baSourceID` field is accessed from index 0 to `bNrInPins` - 1, the current implementation assumes that descriptor is always valid (the length of descriptor is no shorter than 5 + `bNrInPins`). If a descriptor read from the device side is invalid, it may trigger out-of-bound memory access.
struct uac_mixer_unit_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bDescriptorSubtype; __u8 bUnitID; __u8 bNrInPins; __u8 baSourceID[]; }This patch fixes the bug by add a sanity check on the length of the descriptor.
Signed-off-by: Hui Peng benquike@gmail.com Reported-by: Hui Peng benquike@gmail.com Reported-by: Mathias Payer mathias.payer@nebelwelt.net
sound/usb/mixer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 7498b5191b68..38202ce67237 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, struct usb_audio_term iterm; int input_pins, num_ins, num_outs; int pin, ich, err;
int desc_len = (int) ((unsigned long) state->buffer +
state->buflen - (unsigned long) raw_desc);if (desc_len < sizeof(*desc) + desc->bNrInPins) {
usb_audio_err(state->chip,"descriptor %d too short\n",unitid);return -EINVAL;}
err = uac_mixer_unit_get_channels(state, desc); if (err < 0) {
Hm, what is the desc->bLength value in the error case?
Basically the buffer boundary is already checked against bLength in snd_usb_find_desc() which is called from obtaining the raw_desc in the caller of this function (parse_audio_unit()).
So, if any, we need to check bLength for the possible overflow like below.
thanks,
Takashi
--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -744,6 +744,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, return -EINVAL; if (!desc->bNrInPins) return -EINVAL;
- if (desc->bLength < sizeof(*desc) + desc->bNrInPins)
return -EINVAL;
VERSION 1 and 2 already have a different check:
if (desc->bLength < sizeof(*desc) + desc->bNrInPins + 1) return 0; /* no bmControls -> skip */
So something is possibly off by one. It's just version 3 which doesn't have a check.
regards, dan carpenter
On Wed, 14 Aug 2019 11:09:21 +0200, Dan Carpenter wrote:
On Wed, Aug 14, 2019 at 08:36:42AM +0200, Takashi Iwai wrote:
On Wed, 14 Aug 2019 04:36:24 +0200, Hui Peng wrote:
The `uac_mixer_unit_descriptor` shown as below is read from the device side. In `parse_audio_mixer_unit`, `baSourceID` field is accessed from index 0 to `bNrInPins` - 1, the current implementation assumes that descriptor is always valid (the length of descriptor is no shorter than 5 + `bNrInPins`). If a descriptor read from the device side is invalid, it may trigger out-of-bound memory access.
struct uac_mixer_unit_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bDescriptorSubtype; __u8 bUnitID; __u8 bNrInPins; __u8 baSourceID[]; }This patch fixes the bug by add a sanity check on the length of the descriptor.
Signed-off-by: Hui Peng benquike@gmail.com Reported-by: Hui Peng benquike@gmail.com Reported-by: Mathias Payer mathias.payer@nebelwelt.net
sound/usb/mixer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 7498b5191b68..38202ce67237 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, struct usb_audio_term iterm; int input_pins, num_ins, num_outs; int pin, ich, err;
int desc_len = (int) ((unsigned long) state->buffer +
state->buflen - (unsigned long) raw_desc);if (desc_len < sizeof(*desc) + desc->bNrInPins) {
usb_audio_err(state->chip,"descriptor %d too short\n",unitid);return -EINVAL;}
err = uac_mixer_unit_get_channels(state, desc); if (err < 0) {
Hm, what is the desc->bLength value in the error case?
Basically the buffer boundary is already checked against bLength in snd_usb_find_desc() which is called from obtaining the raw_desc in the caller of this function (parse_audio_unit()).
So, if any, we need to check bLength for the possible overflow like below.
thanks,
Takashi
--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -744,6 +744,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, return -EINVAL; if (!desc->bNrInPins) return -EINVAL;
- if (desc->bLength < sizeof(*desc) + desc->bNrInPins)
return -EINVAL;VERSION 1 and 2 already have a different check:
if (desc->bLength < sizeof(*desc) + desc->bNrInPins + 1) return 0; /* no bmControls -> skip */
So something is possibly off by one. It's just version 3 which doesn't have a check.
No, both are sensible checks. The first check is about the minimal size that doesn't contain bmControls bitmap which is optional on some devices, while the latter checks about the presence of bmControls field. Note that the latter returns zero, which means no error, while the former returns an error.
thanks,
Takashi
Hi, Takashi: Here the problem is that `desc->bLength` is controlled by the device side, so `desc->bLength` may not represent the real length of the descriptor. That is why I use pointer arithmetic operations to derive the real size of the buffer in my patch.
On Wed, Aug 14, 2019 at 2:36 AM Takashi Iwai tiwai@suse.de wrote:
On Wed, 14 Aug 2019 04:36:24 +0200, Hui Peng wrote:
The `uac_mixer_unit_descriptor` shown as below is read from the device side. In `parse_audio_mixer_unit`, `baSourceID` field is accessed from index 0 to `bNrInPins` - 1, the current implementation assumes that descriptor is always valid (the length of descriptor is no shorter than 5 + `bNrInPins`). If a descriptor read from the device side is invalid, it may trigger out-of-bound memory access.
struct uac_mixer_unit_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bDescriptorSubtype; __u8 bUnitID; __u8 bNrInPins; __u8 baSourceID[]; }This patch fixes the bug by add a sanity check on the length of the descriptor.
Signed-off-by: Hui Peng benquike@gmail.com Reported-by: Hui Peng benquike@gmail.com Reported-by: Mathias Payer mathias.payer@nebelwelt.net
sound/usb/mixer.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 7498b5191b68..38202ce67237 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct
mixer_build *state, int unitid,
struct usb_audio_term iterm; int input_pins, num_ins, num_outs; int pin, ich, err;
int desc_len = (int) ((unsigned long) state->buffer +state->buflen - (unsigned long) raw_desc);if (desc_len < sizeof(*desc) + desc->bNrInPins) {usb_audio_err(state->chip,"descriptor %d too short\n",unitid);return -EINVAL;} err = uac_mixer_unit_get_channels(state, desc); if (err < 0) {Hm, what is the desc->bLength value in the error case?
Basically the buffer boundary is already checked against bLength in snd_usb_find_desc() which is called from obtaining the raw_desc in the caller of this function (parse_audio_unit()).
So, if any, we need to check bLength for the possible overflow like below.
thanks,
Takashi
--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -744,6 +744,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, return -EINVAL; if (!desc->bNrInPins) return -EINVAL;
if (desc->bLength < sizeof(*desc) + desc->bNrInPins)return -EINVAL; switch (state->mixer->protocol) { case UAC_VERSION_1:
On Wed, 14 Aug 2019 18:28:39 +0200, 彭辉 wrote:
Hi, Takashi: Here the problem is that `desc->bLength` is controlled by the device side, so `desc->bLength` may not represent the real length of the descriptor. That is why I use pointer arithmetic operations to derive the real size of the buffer in my patch.
But bLength is checked before calling this, i.e. it's already assured that bLength fits within the buffer limit. So, the result calls don't have to care about the buffer limit itself, and they can just concentrate on overflow over bLength.
thanks,
Takashi
On Wed, Aug 14, 2019 at 2:36 AM Takashi Iwai tiwai@suse.de wrote:
On Wed, 14 Aug 2019 04:36:24 +0200, Hui Peng wrote: > > The `uac_mixer_unit_descriptor` shown as below is read from the > device side. In `parse_audio_mixer_unit`, `baSourceID` field is > accessed from index 0 to `bNrInPins` - 1, the current implementation > assumes that descriptor is always valid (the length of descriptor > is no shorter than 5 + `bNrInPins`). If a descriptor read from > the device side is invalid, it may trigger out-of-bound memory > access. > > ``` > struct uac_mixer_unit_descriptor { > __u8 bLength; > __u8 bDescriptorType; > __u8 bDescriptorSubtype; > __u8 bUnitID; > __u8 bNrInPins; > __u8 baSourceID[]; > } > ``` > > This patch fixes the bug by add a sanity check on the length of > the descriptor. > > Signed-off-by: Hui Peng <benquike@gmail.com> > Reported-by: Hui Peng <benquike@gmail.com> > Reported-by: Mathias Payer <mathias.payer@nebelwelt.net> > --- > sound/usb/mixer.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c > index 7498b5191b68..38202ce67237 100644 > --- a/sound/usb/mixer.c > +++ b/sound/usb/mixer.c > @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, > struct usb_audio_term iterm; > int input_pins, num_ins, num_outs; > int pin, ich, err; > + int desc_len = (int) ((unsigned long) state->buffer + > + state->buflen - (unsigned long) raw_desc); > + > + if (desc_len < sizeof(*desc) + desc->bNrInPins) { > + usb_audio_err(state->chip, > + "descriptor %d too short\n", > + unitid); > + return -EINVAL; > + } > > err = uac_mixer_unit_get_channels(state, desc); > if (err < 0) { Hm, what is the desc->bLength value in the error case? Basically the buffer boundary is already checked against bLength in snd_usb_find_desc() which is called from obtaining the raw_desc in the caller of this function (parse_audio_unit()). So, if any, we need to check bLength for the possible overflow like below. thanks, Takashi --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -744,6 +744,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, return -EINVAL; if (!desc->bNrInPins) return -EINVAL; + if (desc->bLength < sizeof(*desc) + desc->bNrInPins) + return -EINVAL; switch (state->mixer->protocol) { case UAC_VERSION_1:-- May the Lord Richly Bless you and yours !
Hi, Takashi:
Thanks for the guide. The new patch is confirmed and attached.
On Wed, Aug 14, 2019 at 12:33 PM Takashi Iwai tiwai@suse.de wrote:
On Wed, 14 Aug 2019 18:28:39 +0200, 彭辉 wrote:
Hi, Takashi: Here the problem is that `desc->bLength` is controlled by the device
side,
so `desc->bLength` may not represent the real length of the descriptor. That is why I use pointer arithmetic operations to derive the real size
of the
buffer in my patch.
But bLength is checked before calling this, i.e. it's already assured that bLength fits within the buffer limit. So, the result calls don't have to care about the buffer limit itself, and they can just concentrate on overflow over bLength.
thanks,
Takashi
On Wed, Aug 14, 2019 at 2:36 AM Takashi Iwai tiwai@suse.de wrote:
On Wed, 14 Aug 2019 04:36:24 +0200, Hui Peng wrote: > > The `uac_mixer_unit_descriptor` shown as below is read from the > device side. In `parse_audio_mixer_unit`, `baSourceID` field is > accessed from index 0 to `bNrInPins` - 1, the currentimplementation
> assumes that descriptor is always valid (the length of descriptor > is no shorter than 5 + `bNrInPins`). If a descriptor read from > the device side is invalid, it may trigger out-of-bound memory > access. > > ``` > struct uac_mixer_unit_descriptor { > __u8 bLength; > __u8 bDescriptorType; > __u8 bDescriptorSubtype; > __u8 bUnitID; > __u8 bNrInPins; > __u8 baSourceID[]; > } > ``` > > This patch fixes the bug by add a sanity check on the length of > the descriptor. > > Signed-off-by: Hui Peng <benquike@gmail.com> > Reported-by: Hui Peng <benquike@gmail.com> > Reported-by: Mathias Payer <mathias.payer@nebelwelt.net> > --- > sound/usb/mixer.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c > index 7498b5191b68..38202ce67237 100644 > --- a/sound/usb/mixer.c > +++ b/sound/usb/mixer.c > @@ -2091,6 +2091,15 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid, > struct usb_audio_term iterm; > int input_pins, num_ins, num_outs; > int pin, ich, err; > + int desc_len = (int) ((unsigned long) state->buffer + > + state->buflen - (unsigned long) raw_desc); > + > + if (desc_len < sizeof(*desc) + desc->bNrInPins) { > + usb_audio_err(state->chip, > + "descriptor %d too short\n", > + unitid); > + return -EINVAL; > + } > > err = uac_mixer_unit_get_channels(state, desc); > if (err < 0) { Hm, what is the desc->bLength value in the error case? Basically the buffer boundary is already checked against bLength in snd_usb_find_desc() which is called from obtaining the raw_desc inthe
caller of this function (parse_audio_unit()). So, if any, we need to check bLength for the possible overflow like below. thanks, Takashi --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -744,6 +744,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state, return -EINVAL; if (!desc->bNrInPins) return -EINVAL; + if (desc->bLength < sizeof(*desc) + desc->bNrInPins) + return -EINVAL; switch (state->mixer->protocol) { case UAC_VERSION_1:-- May the Lord Richly Bless you and yours !
participants (4)
-
Dan Carpenter -
Hui Peng -
Takashi Iwai -
彭辉