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ALSA: usb-audio: Check mixer unit descriptors more strictly

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We've had some sanity checks of the mixer unit descriptors but they
are too loose and some corner cases are overlooked.  Add more strict
checks in uac_mixer_unit_get_channels() for avoiding possible OOB
accesses by malformed descriptors.

This also changes the semantics of uac_mixer_unit_get_channels()
slightly.  Now it returns zero for the cases where the descriptor
lacks of bmControls instead of -EINVAL.  Then the caller side skips
the mixer creation for such unit while it keeps parsing it.
This corresponds to the case like Maya44.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2018-12-19 14:04:47 +01:00
parent f4351a199c
commit 0bfe5e434e
1 changed files with 11 additions and 4 deletions
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15
sound/usb/mixer.c
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@ -753,8 +753,9 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state,
struct uac_mixer_unit_descriptor *desc)
{
int mu_channels;
void *c;
if (desc->bLength < 11)
if (desc->bLength < sizeof(*desc))
return -EINVAL;
if (!desc->bNrInPins)
return -EINVAL;
@ -763,6 +764,8 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state,
case UAC_VERSION_1:
case UAC_VERSION_2:
default:
if (desc->bLength < sizeof(*desc) + desc->bNrInPins + 1)
return 0; /* no bmControls -> skip */
mu_channels = uac_mixer_unit_bNrChannels(desc);
break;
case UAC_VERSION_3:
@ -772,7 +775,11 @@ static int uac_mixer_unit_get_channels(struct mixer_build *state,
}
if (!mu_channels)
return -EINVAL;
return 0;
c = uac_mixer_unit_bmControls(desc, state->mixer->protocol);
if (c - (void *)desc + (mu_channels - 1) / 8 >= desc->bLength)
return 0; /* no bmControls -> skip */
return mu_channels;
}
@ -944,7 +951,7 @@ static int check_input_term(struct mixer_build *state, int id,
struct uac_mixer_unit_descriptor *d = p1;
err = uac_mixer_unit_get_channels(state, d);
if (err < 0)
if (err <= 0)
return err;
term->channels = err;
@ -2118,7 +2125,7 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid,
if (err < 0)
continue;
/* no bmControls field (e.g. Maya44) -> ignore */
if (desc->bLength <= 10 + input_pins)
if (!num_outs)
continue;
err = check_input_term(state, desc->baSourceID[pin], &iterm);
if (err < 0)