Fix multiple cases of out of bounds (OOB) read associated with
MCE device receive/input data handling.
In reference for the OOB cases below, the incoming/read (byte) data
format when the MCE device responds to a command is:
{ cmd_prefix, subcmd, data0, data1, ... }
where cmd_prefix are:
MCE_CMD_PORT_SYS
MCE_CMD_PORT_IR
and subcmd examples are:
MCE_RSP_GETPORTSTATUS
MCE_RSP_EQIRNUMPORTS
...
Response size dynamically depends on cmd_prefix and subcmd.
So data0, data1, ... may or may not be present on input.
Multiple responses may return in a single receiver buffer.
The trigger condition for OOB read is typically random or
corrupt input data that fills the mceusb receiver buffer.
Case 1:
mceusb_handle_command() reads data0 (var hi) and data1 (var lo)
regardless of whether the response includes such data.
If { cmd_prefix, subcmd } is at the end of the receiver buffer,
read past end of buffer occurs.
This case was reported by
KASAN: slab-out-of-bounds Read in mceusb_dev_recv
https://syzkaller.appspot.com/bug?extid=c7fdb6cb36e65f2fe8c9
Fix: In mceusb_handle_command(), change variable hi and lo to
pointers, and dereference only when required.
Case 2:
If response with data is truncated at end of buffer after
{ cmd_prefix, subcmd }, mceusb_handle_command() reads past
end of buffer for data0, data1, ...
Fix: In mceusb_process_ir_data(), check response size with
remaining buffer size before invoking mceusb_handle_command().
+ if (i + ir->rem < buf_len)
mceusb_handle_command(ir, &ir->buf_in[i - 1]);
Case 3:
mceusb_handle_command() handles invalid/bad response such as
{ 0x??, MCE_RSP_GETPORTSTATUS } of length 2 as a response
{ MCE_CMD_PORT_SYS, MCE_RSP_GETPORTSTATUS, data0, ... }
of length 7. Read OOB occurs for non-existent data0, data1, ...
Cause is mceusb_handle_command() does not check cmd_prefix value.
Fix: mceusb_handle_command() must test both cmd_prefix and subcmd.
Case 4:
mceusb_process_ir_data() receiver parser state SUBCMD is
possible at start (i=0) of receiver buffer resulting in buffer
offset=-1 passed to mceusb_dev_printdata().
Bad offset results in OOB read before start of buffer.
[1214218.580308] mceusb 1-1.3:1.0: rx data[0]: 00 80 (length=2)
[1214218.580323] mceusb 1-1.3:1.0: Unknown command 0x00 0x80
...
[1214218.580406] mceusb 1-1.3:1.0: rx data[14]: 7f 7f (length=2)
[1214218.679311] mceusb 1-1.3:1.0: rx data[-1]: 80 90 (length=2)
[1214218.679325] mceusb 1-1.3:1.0: End of raw IR data
[1214218.679340] mceusb 1-1.3:1.0: rx data[1]: 7f 7f (length=2)
Fix: If parser_state is SUBCMD after processing receiver buffer,
reset parser_state to CMD_HEADER.
In effect, discard cmd_prefix at end of receiver buffer.
In mceusb_dev_printdata(), abort if buffer offset is out of bounds.
Case 5:
If response with data is truncated at end of buffer after
{ cmd_prefix, subcmd }, mceusb_dev_printdata() reads past
end of buffer for data0, data1, ...
while decoding the response to print out.
Fix: In mceusb_dev_printdata(), remove unneeded buffer offset
adjustments (var start and var skip) associated with MCE gen1 header.
Test for truncated MCE cmd response (compare offset+len with buf_len)
and skip decoding of incomplete response.
Move IR data tracing to execute before the truncation test.
Signed-off-by: A Sun <as1033x@xxxxxxxxxxx>
---
drivers/media/rc/mceusb.c | 141 ++++++++++++++++++++++++++++++++--------------
1 file changed, 98 insertions(+), 43 deletions(-)
diff --git a/drivers/media/rc/mceusb.c b/drivers/media/rc/mceusb.c
index f9ed855e2..9c1cf53b0 100644
--- a/drivers/media/rc/mceusb.c
+++ b/drivers/media/rc/mceusb.c
@@ -559,7 +559,7 @@ static int mceusb_cmd_datasize(u8 cmd, u8 subcmd)
datasize = 4;
break;
case MCE_CMD_G_REVISION:
- datasize = 2;
+ datasize = 4;
break;
case MCE_RSP_EQWAKESUPPORT:
case MCE_RSP_GETWAKESOURCE:
@@ -595,14 +595,9 @@ static void mceusb_dev_printdata(struct mceusb_dev *ir, u8 *buf, int buf_len,
char *inout;
u8 cmd, subcmd, *data;
struct device *dev = ir->dev;
- int start, skip = 0;
u32 carrier, period;
- /* skip meaningless 0xb1 0x60 header bytes on orig receiver */
- if (ir->flags.microsoft_gen1 && !out && !offset)
- skip = 2;
-
- if (len <= skip)
+ if (offset < 0 || offset >= buf_len)
return;
dev_dbg(dev, "%cx data[%d]: %*ph (len=%d sz=%d)",
@@ -611,11 +606,32 @@ static void mceusb_dev_printdata(struct mceusb_dev *ir, u8 *buf, int buf_len,
inout = out ? "Request" : "Got";
- start = offset + skip;
- cmd = buf[start] & 0xff;
- subcmd = buf[start + 1] & 0xff;
- data = buf + start + 2;
+ cmd = buf[offset];
+ subcmd = (offset + 1 < buf_len) ? buf[offset + 1] : 0;
+ data = &buf[offset] + 2;
+
+ /* Trace meaningless 0xb1 0x60 header bytes on original receiver */
+ if (ir->flags.microsoft_gen1 && !out && !offset) {
+ dev_dbg(dev, "MCE gen 1 header");
+ return;
+ }
+
+ /* Trace IR data header or trailer */
+ if (cmd != MCE_CMD_PORT_IR &&
+ (cmd & MCE_PORT_MASK) == MCE_COMMAND_IRDATA) {
+ if (cmd == MCE_IRDATA_TRAILER)
+ dev_dbg(dev, "End of raw IR data");
+ else
+ dev_dbg(dev, "Raw IR data, %d pulse/space samples",
+ cmd & MCE_PACKET_LENGTH_MASK);
+ return;
+ }
+
+ /* Unexpected end of buffer? */
+ if (offset + len > buf_len)
+ return;
+ /* Decode MCE command/response */
switch (cmd) {
case MCE_CMD_NULL:
if (subcmd == MCE_CMD_NULL)
@@ -639,7 +655,7 @@ static void mceusb_dev_printdata(struct mceusb_dev *ir, u8 *buf, int buf_len,
dev_dbg(dev, "Get hw/sw rev?");
else
dev_dbg(dev, "hw/sw rev %*ph",
- 4, &buf[start + 2]);
+ 4, &buf[offset + 2]);
break;
case MCE_CMD_RESUME:
dev_dbg(dev, "Device resume requested");
@@ -741,13 +757,6 @@ static void mceusb_dev_printdata(struct mceusb_dev *ir, u8 *buf, int buf_len,
default:
break;
}
-
- if (cmd == MCE_IRDATA_TRAILER)
- dev_dbg(dev, "End of raw IR data");
- else if ((cmd != MCE_CMD_PORT_IR) &&
- ((cmd & MCE_PORT_MASK) == MCE_COMMAND_IRDATA))
- dev_dbg(dev, "Raw IR data, %d pulse/space samples",
- cmd & MCE_PACKET_LENGTH_MASK);
#endif
}
@@ -1131,32 +1140,62 @@ static int mceusb_set_rx_carrier_report(struct rc_dev *dev, int enable)
}
/*
+ * Handle PORT_SYS/IR command response received from the MCE device.
+ *
+ * Assumes single response with all its data (not truncated)
+ * in buf_in[]. The response itself determines its total length
+ * (mceusb_cmd_datasize() + 2) and hence the minimum size of buf_in[].
+ *
* We don't do anything but print debug spew for many of the command bits
* we receive from the hardware, but some of them are useful information
* we want to store so that we can use them.
*/
-static void mceusb_handle_command(struct mceusb_dev *ir, int index)
+static void mceusb_handle_command(struct mceusb_dev *ir, u8 *buf_in)
{
+ u8 cmd = buf_in[0];
+ u8 subcmd = buf_in[1];
+ u8 *hi = &buf_in[2]; /* read only when required */
+ u8 *lo = &buf_in[3]; /* read only when required */
struct ir_raw_event rawir = {};
- u8 hi = ir->buf_in[index + 1] & 0xff;
- u8 lo = ir->buf_in[index + 2] & 0xff;
u32 carrier_cycles;
u32 cycles_fix;
- switch (ir->buf_in[index]) {
- /* the one and only 5-byte return value command */
- case MCE_RSP_GETPORTSTATUS:
- if ((ir->buf_in[index + 4] & 0xff) == 0x00)
- ir->txports_cabled |= 1 << hi;
- break;
+ if (cmd == MCE_CMD_PORT_SYS) {
+ switch (subcmd) {
+ /* the one and only 5-byte return value command */
+ case MCE_RSP_GETPORTSTATUS:
+ if (buf_in[5] == 0)
+ ir->txports_cabled |= 1 << *hi;
+ break;
+
+ /* 1-byte return value commands */
+ case MCE_RSP_EQEMVER:
+ ir->emver = *hi;
+ break;
+
+ /* No return value commands */
+ case MCE_RSP_CMD_ILLEGAL:
+ ir->need_reset = true;
+ break;
+
+ default:
+ break;
+ }
+
+ return;
+ }
+ if (cmd != MCE_CMD_PORT_IR)
+ return;
+
+ switch (subcmd) {
/* 2-byte return value commands */
case MCE_RSP_EQIRTIMEOUT:
- ir->rc->timeout = US_TO_NS((hi << 8 | lo) * MCE_TIME_UNIT);
+ ir->rc->timeout = US_TO_NS((*hi << 8 | *lo) * MCE_TIME_UNIT);
break;
case MCE_RSP_EQIRNUMPORTS:
- ir->num_txports = hi;
- ir->num_rxports = lo;
+ ir->num_txports = *hi;
+ ir->num_rxports = *lo;
break;
case MCE_RSP_EQIRRXCFCNT:
/*
@@ -1169,7 +1208,7 @@ static void mceusb_handle_command(struct mceusb_dev *ir, int index)
*/
if (ir->carrier_report_enabled && ir->learning_active &&
ir->pulse_tunit > 0) {
- carrier_cycles = (hi << 8 | lo);
+ carrier_cycles = (*hi << 8 | *lo);
/*
* Adjust carrier cycle count by adding
* 1 missed count per pulse "on"
@@ -1187,24 +1226,24 @@ static void mceusb_handle_command(struct mceusb_dev *ir, int index)
break;
/* 1-byte return value commands */
- case MCE_RSP_EQEMVER:
- ir->emver = hi;
- break;
case MCE_RSP_EQIRTXPORTS:
- ir->tx_mask = hi;
+ ir->tx_mask = *hi;
break;
case MCE_RSP_EQIRRXPORTEN:
- ir->learning_active = ((hi & 0x02) == 0x02);
- if (ir->rxports_active != hi) {
+ ir->learning_active = ((*hi & 0x02) == 0x02);
+ if (ir->rxports_active != *hi) {
dev_info(ir->dev, "%s-range (0x%x) receiver active",
- ir->learning_active ? "short" : "long", hi);
- ir->rxports_active = hi;
+ ir->learning_active ? "short" : "long", *hi);
+ ir->rxports_active = *hi;
}
break;
+
+ /* No return value commands */
case MCE_RSP_CMD_ILLEGAL:
case MCE_RSP_TX_TIMEOUT:
ir->need_reset = true;
break;
+
default:
break;
}
@@ -1230,7 +1269,8 @@ static void mceusb_process_ir_data(struct mceusb_dev *ir, int buf_len)
ir->rem = mceusb_cmd_datasize(ir->cmd, ir->buf_in[i]);
mceusb_dev_printdata(ir, ir->buf_in, buf_len, i - 1,
ir->rem + 2, false);
- mceusb_handle_command(ir, i);
+ if (i + ir->rem < buf_len)
+ mceusb_handle_command(ir, &ir->buf_in[i - 1]);
ir->parser_state = CMD_DATA;
break;
case PARSE_IRDATA:
@@ -1259,15 +1299,22 @@ static void mceusb_process_ir_data(struct mceusb_dev *ir, int buf_len)
ir->rem--;
break;
case CMD_HEADER:
- /* decode mce packets of the form (84),AA,BB,CC,DD */
- /* IR data packets can span USB messages - rem */
ir->cmd = ir->buf_in[i];
if ((ir->cmd == MCE_CMD_PORT_IR) ||
((ir->cmd & MCE_PORT_MASK) !=
MCE_COMMAND_IRDATA)) {
+ /*
+ * got PORT_SYS, PORT_IR, or unknown
+ * command response prefix
+ */
ir->parser_state = SUBCMD;
continue;
}
+ /*
+ * got IR data prefix (0x80 + num_bytes)
+ * decode MCE packets of the form {0x83, AA, BB, CC}
+ * IR data packets can span USB messages
+ */
ir->rem = (ir->cmd & MCE_PACKET_LENGTH_MASK);
mceusb_dev_printdata(ir, ir->buf_in, buf_len,
i, ir->rem + 1, false);
@@ -1291,6 +1338,14 @@ static void mceusb_process_ir_data(struct mceusb_dev *ir, int buf_len)
if (ir->parser_state != CMD_HEADER && !ir->rem)
ir->parser_state = CMD_HEADER;
}
+
+ /*
+ * Accept IR data spanning multiple rx buffers.
+ * Reject MCE command response spanning multiple rx buffers.
+ */
+ if (ir->parser_state != PARSE_IRDATA || !ir->rem)
+ ir->parser_state = CMD_HEADER;
+
if (event) {
dev_dbg(ir->dev, "processed IR data");
ir_raw_event_handle(ir->rc);
--
2.11.0
