0x7d and 0x7e bytes are meant to be escaped in the data portion of
frames, but this didn't occur since next_chunk_len() had an off-by-one
error. That also resulted in the final byte of a payload being written
as a separate tty write op.
The chunk prior to an escaped byte would be one byte short, and the
next call would never test the txpos+1 case, which is where the escaped
byte was located. That meant it never hit the escaping case in
mctp_serial_tx_work().
Example Input: 01 00 08 c8 7e 80 02
Previous incorrect chunks from next_chunk_len():
01 00 08
c8 7e 80
02
With this fix:
01 00 08 c8
7e
80 02
Cc: stable@xxxxxxxxxxxxxxx
Fixes: a0c2ccd9b5ad ("mctp: Add MCTP-over-serial transport binding")
Signed-off-by: Matt Johnston <matt@xxxxxxxxxxxxxxxxxxxx>
---
drivers/net/mctp/mctp-serial.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/mctp/mctp-serial.c b/drivers/net/mctp/mctp-serial.c
index d7db11355909..82890e983847 100644
--- a/drivers/net/mctp/mctp-serial.c
+++ b/drivers/net/mctp/mctp-serial.c
@@ -91,8 +91,8 @@ static int next_chunk_len(struct mctp_serial *dev)
* will be those non-escaped bytes, and does not include the escaped
* byte.
*/
- for (i = 1; i + dev->txpos + 1 < dev->txlen; i++) {
- if (needs_escape(dev->txbuf[dev->txpos + i + 1]))
+ for (i = 1; i + dev->txpos < dev->txlen; i++) {
+ if (needs_escape(dev->txbuf[dev->txpos + i]))
break;
}
