* [PATCH] media: ttusb-dec: validate command response length
@ 2026-08-16 7:08 George Emmanuel Thomas
2026-08-16 7:31 ` George Emmanuel Thomas
0 siblings, 1 reply; 2+ messages in thread
From: George Emmanuel Thomas @ 2026-08-16 7:08 UTC (permalink / raw)
To: mchehab; +Cc: kees, linux-media, linux-kernel, George Emmanuel Thomas
ttusb_dec_send_command() uses a length supplied by the USB device to
copy command response data without validating it against the amount of
data actually received. A malformed device can therefore cause an
out-of-bounds read from the response buffer.
The helper also does not know the size of the caller-provided response
buffer. This can cause an out-of-bounds write when the device reports a
response larger than the destination buffer.
Pass the destination buffer size to ttusb_dec_send_command() and reject
responses whose payload exceeds either the received data or the
destination buffer.
Signed-off-by: George Emmanuel Thomas <georgeemmanuelthomas@gmail.com>
---
drivers/media/usb/ttusb-dec/ttusb_dec.c | 42 ++++++++++++++++--------
drivers/media/usb/ttusb-dec/ttusbdecfe.c | 9 ++---
drivers/media/usb/ttusb-dec/ttusbdecfe.h | 3 +-
3 files changed, 36 insertions(+), 18 deletions(-)
diff --git a/drivers/media/usb/ttusb-dec/ttusb_dec.c b/drivers/media/usb/ttusb-dec/ttusb_dec.c
index 825a3875989d..2701e9275724 100644
--- a/drivers/media/usb/ttusb-dec/ttusb_dec.c
+++ b/drivers/media/usb/ttusb-dec/ttusb_dec.c
@@ -314,7 +314,8 @@ static u16 crc16(u16 crc, const u8 *buf, size_t len)
static int ttusb_dec_send_command(struct ttusb_dec *dec, const u8 command,
int param_length, const u8 params[],
- int *result_length, u8 cmd_result[])
+ int *result_length, u8 cmd_result[],
+ size_t cmd_result_size)
{
int result, actual_len;
u8 *b;
@@ -366,6 +367,15 @@ static int ttusb_dec_send_command(struct ttusb_dec *dec, const u8 command,
__func__, actual_len, b);
}
+ if (actual_len < 4 || b[3] > actual_len - 4) {
+ result = -EIO;
+ goto err_mutex_unlock;
+ }
+
+ if (cmd_result && b[3] > cmd_result_size) {
+ result = -EIO;
+ goto err_mutex_unlock;
+ }
if (result_length)
*result_length = b[3];
if (cmd_result && b[3] > 0)
@@ -389,7 +399,8 @@ static int ttusb_dec_get_stb_state (struct ttusb_dec *dec, unsigned int *mode,
dprintk("%s\n", __func__);
- result = ttusb_dec_send_command(dec, 0x08, 0, NULL, &c_length, c);
+ result = ttusb_dec_send_command(dec, 0x08, 0, NULL, &c_length, c,
+ sizeof(c));
if (result)
return result;
@@ -448,7 +459,7 @@ static void ttusb_dec_set_pids(struct ttusb_dec *dec)
memcpy(&b[2], &audio, 2);
memcpy(&b[4], &video, 2);
- ttusb_dec_send_command(dec, 0x50, sizeof(b), b, NULL, NULL);
+ ttusb_dec_send_command(dec, 0x50, sizeof(b), b, NULL, NULL, 0);
dvb_filter_pes2ts_init(&dec->a_pes2ts, dec->pid[DMX_PES_AUDIO],
ttusb_dec_audio_pes2ts_cb, dec);
@@ -902,7 +913,7 @@ static int ttusb_dec_set_interface(struct ttusb_dec *dec,
break;
case TTUSB_DEC_INTERFACE_IN:
result = ttusb_dec_send_command(dec, 0x80, sizeof(b),
- b, NULL, NULL);
+ b, NULL, NULL, 0);
if (result)
return result;
result = usb_set_interface(dec->udev, 0, 8);
@@ -1021,7 +1032,8 @@ static int ttusb_dec_start_ts_feed(struct dvb_demux_feed *dvbdmxfeed)
}
- result = ttusb_dec_send_command(dec, 0x80, sizeof(b0), b0, NULL, NULL);
+ result = ttusb_dec_send_command(dec, 0x80, sizeof(b0), b0,
+ NULL, NULL, 0);
if (result)
return result;
@@ -1056,7 +1068,7 @@ static int ttusb_dec_start_sec_feed(struct dvb_demux_feed *dvbdmxfeed)
memcpy(&b0[5], &dvbdmxfeed->filter->filter.filter_value[0], 1);
result = ttusb_dec_send_command(dec, 0x60, sizeof(b0), b0,
- &c_length, c);
+ &c_length, c, sizeof(c));
if (!result) {
if (c_length == 2) {
@@ -1114,7 +1126,7 @@ static int ttusb_dec_stop_ts_feed(struct dvb_demux_feed *dvbdmxfeed)
struct ttusb_dec *dec = dvbdmxfeed->demux->priv;
u8 b0[] = { 0x00 };
- ttusb_dec_send_command(dec, 0x81, sizeof(b0), b0, NULL, NULL);
+ ttusb_dec_send_command(dec, 0x81, sizeof(b0), b0, NULL, NULL, 0);
dec->pva_stream_count--;
@@ -1135,7 +1147,7 @@ static int ttusb_dec_stop_sec_feed(struct dvb_demux_feed *dvbdmxfeed)
list_del(&finfo->filter_info_list);
spin_unlock_irqrestore(&dec->filter_info_list_lock, flags);
kfree(finfo);
- ttusb_dec_send_command(dec, 0x62, sizeof(b0), b0, NULL, NULL);
+ ttusb_dec_send_command(dec, 0x62, sizeof(b0), b0, NULL, NULL, 0);
dec->filter_stream_count--;
@@ -1238,7 +1250,7 @@ static int ttusb_init_rc( struct ttusb_dec *dec)
if (usb_submit_urb(dec->irq_urb, GFP_KERNEL))
printk("%s: usb_submit_urb failed\n",__func__);
/* enable irq pipe */
- ttusb_dec_send_command(dec,0xb0,sizeof(b),b,NULL,NULL);
+ ttusb_dec_send_command(dec, 0xb0, sizeof(b), b, NULL, NULL, 0);
return 0;
}
@@ -1354,7 +1366,8 @@ static int ttusb_dec_boot_dsp(struct ttusb_dec *dec)
firmware_csum_ns = htons(firmware_csum);
memcpy(&b0[6], &firmware_csum_ns, 2);
- result = ttusb_dec_send_command(dec, 0x41, sizeof(b0), b0, NULL, NULL);
+ result = ttusb_dec_send_command(dec, 0x41, sizeof(b0), b0,
+ NULL, NULL, 0);
if (result) {
release_firmware(fw_entry);
@@ -1395,7 +1408,8 @@ static int ttusb_dec_boot_dsp(struct ttusb_dec *dec)
}
}
- result = ttusb_dec_send_command(dec, 0x43, sizeof(b1), b1, NULL, NULL);
+ result = ttusb_dec_send_command(dec, 0x43, sizeof(b1), b1,
+ NULL, NULL, 0);
release_firmware(fw_entry);
kfree(b);
@@ -1621,10 +1635,12 @@ static void ttusb_dec_exit_filters(struct ttusb_dec *dec)
static int fe_send_command(struct dvb_frontend* fe, const u8 command,
int param_length, const u8 params[],
- int *result_length, u8 cmd_result[])
+ int *result_length, u8 cmd_result[],
+ size_t cmd_result_size)
{
struct ttusb_dec* dec = fe->dvb->priv;
- return ttusb_dec_send_command(dec, command, param_length, params, result_length, cmd_result);
+ return ttusb_dec_send_command(dec, command, param_length, params,
+ result_length, cmd_result, cmd_result_size);
}
static const struct ttusbdecfe_config fe_config = {
diff --git a/drivers/media/usb/ttusb-dec/ttusbdecfe.c b/drivers/media/usb/ttusb-dec/ttusbdecfe.c
index 215221370c19..1c2892a1e268 100644
--- a/drivers/media/usb/ttusb-dec/ttusbdecfe.c
+++ b/drivers/media/usb/ttusb-dec/ttusbdecfe.c
@@ -44,7 +44,8 @@ static int ttusbdecfe_dvbt_read_status(struct dvb_frontend *fe,
*status=0;
- ret=state->config->send_command(fe, 0x73, sizeof(b), b, &len, result);
+ ret = state->config->send_command(fe, 0x73, sizeof(b), b, &len,
+ result, sizeof(result));
if(ret)
return ret;
@@ -85,7 +86,7 @@ static int ttusbdecfe_dvbt_set_frontend(struct dvb_frontend *fe)
__be32 freq = htonl(p->frequency / 1000);
memcpy(&b[4], &freq, sizeof (u32));
- state->config->send_command(fe, 0x71, sizeof(b), b, NULL, NULL);
+ state->config->send_command(fe, 0x71, sizeof(b), b, NULL, NULL, 0);
return 0;
}
@@ -130,7 +131,7 @@ static int ttusbdecfe_dvbs_set_frontend(struct dvb_frontend *fe)
lnb_voltage = htonl(state->voltage);
memcpy(&b[28], &lnb_voltage, sizeof(u32));
- state->config->send_command(fe, 0x71, sizeof(b), b, NULL, NULL);
+ state->config->send_command(fe, 0x71, sizeof(b), b, NULL, NULL, 0);
return 0;
}
@@ -149,7 +150,7 @@ static int ttusbdecfe_dvbs_diseqc_send_master_cmd(struct dvb_frontend* fe, struc
state->config->send_command(fe, 0x72,
sizeof(b) - (6 - cmd->msg_len), b,
- NULL, NULL);
+ NULL, NULL, 0);
return 0;
}
diff --git a/drivers/media/usb/ttusb-dec/ttusbdecfe.h b/drivers/media/usb/ttusb-dec/ttusbdecfe.h
index 73828bb2258c..b757e093365c 100644
--- a/drivers/media/usb/ttusb-dec/ttusbdecfe.h
+++ b/drivers/media/usb/ttusb-dec/ttusbdecfe.h
@@ -14,7 +14,8 @@ struct ttusbdecfe_config
{
int (*send_command)(struct dvb_frontend* fe, const u8 command,
int param_length, const u8 params[],
- int *result_length, u8 cmd_result[]);
+ int *result_length, u8 cmd_result[],
+ size_t cmd_result_size);
};
extern struct dvb_frontend* ttusbdecfe_dvbs_attach(const struct ttusbdecfe_config* config);
--
2.53.0
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2026-08-16 7:08 [PATCH] media: ttusb-dec: validate command response length George Emmanuel Thomas
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