From: Takashi Iwai <tiwai@suse.de>
To: "Hui Peng" <benquike@gmail.com>
Cc: <security@kernel.org>, <alsa-devel@alsa-project.org>,
"YueHaibing" <yuehaibing@huawei.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Allison Randal" <allison@lohutok.net>,
"Mathias Payer" <mathias.payer@nebelwelt.net>,
"Jaroslav Kysela" <perex@perex.cz>,
"Takashi Iwai" <tiwai@suse.com>, "Wenwen Wang" <wang6495@umn.edu>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Fix an OOB bug in parse_audio_mixer_unit
Date: Wed, 14 Aug 2019 08:36:42 +0200 [thread overview]
Message-ID: <s5hzhkcb6dh.wl-tiwai@suse.de> (raw)
In-Reply-To: <20190814023625.21683-1-benquike@gmail.com>
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:
next prev parent reply other threads:[~2019-08-14 6:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 2:36 [PATCH] Fix an OOB bug in parse_audio_mixer_unit Hui Peng
2019-08-14 6:36 ` Takashi Iwai [this message]
2019-08-14 9:09 ` Dan Carpenter
2019-08-14 15:14 ` Takashi Iwai
[not found] ` <CAKpmkkUv=arsdJiexaM-UVhXEwfGN=zreny9P_kDNhQUij8=FQ@mail.gmail.com>
2019-08-14 16:33 ` Takashi Iwai
[not found] ` <CAKpmkkVzT5H0RTAu_Fa=9_gjf5v7k3qzPnnJvPpBp3BaP7G0ag@mail.gmail.com>
2019-08-14 18:21 ` Takashi Iwai
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