[alsa-devel] [PATCH] Fix an OOB bug in parse_audio_mixer_unit

[彭辉]

The attached file is the KASAN report.

On Tue, Aug 13, 2019 at 10:37 PM Hui Peng <benquike at 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 at gmail.com>
> Reported-by: Hui Peng <benquike at gmail.com>
> Reported-by: Mathias Payer <mathias.payer at 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
>
>

-- 
May the *Lord* Richly Bless you and yours !
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bug-0813.kasan.report
Type: application/octet-stream
Size: 11237 bytes
Desc: not available
URL: <http://mailman.alsa-project.org/pipermail/alsa-devel/attachments/20190813/3d3eb67d/attachment-0001.obj>