[PATCH RFC] media: ttusb-dec: fix buffer overflow in ttusb_dec_send_command()
"syzbot" <[email protected]> Sun, 2 Aug 2026 20:47:10 +0000 (UTC)
| Newsgroups | dev.linux.lists.syzbot |
|---|---|
| Message-ID | <[email protected]> |
The `ttusb_dec_send_command()` function sends a command to the USB device
and reads back the response into a dynamically allocated buffer. If the
bulk message succeeds, the function blindly trusts `b[3]` (which is
controlled by the USB device) as the length of the payload to copy into the
caller-provided `cmd_result` buffer.
This leads to two distinct buffer overflow issues. First, a read overflow:
the buffer `b` is 64 bytes long, meaning the payload starting at `&b[4]`
has exactly 60 bytes of space. If the device sends a packet where `b[3] >
60`, `memcpy()` will read past the end of the `b` buffer. Second, a write
overflow: the function has no knowledge of the size of the `cmd_result`
buffer provided by the caller. In `ttusb_dec_get_stb_state()`, the buffer
is 60 bytes on the stack. In `ttusbdecfe_dvbt_read_status()`, the buffer is
only 4 bytes. A length greater than the buffer size will result in a stack
buffer overflow.
This issue can be observed in the following crash report:
------------[ cut here ]------------
memcpy: detected buffer overflow: 75 byte read of buffer size 60
WARNING: lib/string_helpers.c:1037 at __fortify_report+0x6b/0xa0
lib/string_helpers.c:1036, CPU#1: kworker/1:1/38
...
Call Trace:
<TASK>
__fortify_panic+0x9/0x10 lib/string_helpers.c:1043
fortify_memcpy_chk include/linux/fortify-string.h:549 [inline]
ttusb_dec_send_command+0x681/0x690
drivers/media/usb/ttusb-dec/ttusb_dec.c:372
ttusb_dec_get_stb_state drivers/media/usb/ttusb-dec/ttusb_dec.c:392
[inline]
ttusb_dec_init_stb drivers/media/usb/ttusb-dec/ttusb_dec.c:1413 [inline]
ttusb_dec_probe+0x8e4/0x2160 drivers/media/usb/ttusb-dec/ttusb_dec.c:1671
usb_probe_interface+0x653/0xc60 drivers/usb/core/driver.c:396
...
To fix this, update the API signature of `ttusb_dec_send_command()` and the
`send_command` callback to take the destination buffer length
(`cmd_result_len`). Add validation in `ttusb_dec_send_command()` to ensure
the length field `b[3]` does not exceed the actual received USB packet
length and the destination buffer size. Update all callers to pass the
correct buffer size.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=ac9880be0b0b1a5f54d6
Link: https://syzkaller.appspot.com/ai_job?id=fb923fb6-2d12-42a7-a06c-83685d3f6461
To: <[email protected]>
To: "Mauro Carvalho Chehab" <[email protected]>
To: "Linus Torvalds" <[email protected]>
Cc: "Kees Cook" <[email protected]>
Cc: <[email protected]>
---
diff --git a/drivers/media/usb/ttusb-dec/ttusb_dec.c b/drivers/media/usb/ttusb-dec/ttusb_dec.c
index 825a38759..41e9501cd 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[],
+ int cmd_result_len)
{
int result, actual_len;
u8 *b;
@@ -361,15 +362,26 @@ static int ttusb_dec_send_command(struct ttusb_dec *dec, const u8 command,
__func__, result);
goto err_mutex_unlock;
} else {
+ int rlen = 0;
+
if (debug) {
printk(KERN_DEBUG "%s: result: %*ph\n",
__func__, actual_len, b);
}
+ if (actual_len >= 4) {
+ rlen = b[3];
+ if (rlen > actual_len - 4)
+ rlen = actual_len - 4;
+ }
+
+ if (cmd_result && rlen > cmd_result_len)
+ rlen = cmd_result_len;
+
if (result_length)
- *result_length = b[3];
- if (cmd_result && b[3] > 0)
- memcpy(cmd_result, &b[4], b[3]);
+ *result_length = rlen;
+ if (cmd_result && rlen > 0)
+ memcpy(cmd_result, &b[4], rlen);
}
err_mutex_unlock:
@@ -389,7 +401,8 @@ 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 +461,7 @@ 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 +915,7 @@ 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 +1034,7 @@ 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 +1069,7 @@ 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 +1127,7 @@ 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 +1148,7 @@ 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 +1251,7 @@ 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 +1367,7 @@ 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 +1408,7 @@ 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 +1634,14 @@ 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[],
+ int cmd_result_len)
{
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_len);
}
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 215221370..b013d6dfc 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 73828bb22..96600ad4c 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[],
+ int cmd_result_len);
};
extern struct dvb_frontend* ttusbdecfe_dvbs_attach(const struct ttusbdecfe_config* config);
base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff
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