[PATCH 4.9 37/66] tty: n_gsm: fix malformed counter for out of frame data

Greg Kroah-Hartman
2022-05-10T13:14:20Z

From: Daniel Starke <daniel.starke@siemens.com>

commit a24b4b2f660b7ddf3f484b37600bba382cb28a9d upstream.

The gsm_mux field 'malformed' represents the number of malformed frames
received. However, gsm1_receive() also increases this counter for any out
of frame byte.
Fix this by ignoring out of frame data for the malformed counter.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220414094225.4527-7-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/n_gsm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1977,7 +1977,8 @@ static void gsm1_receive(struct gsm_mux
}
/* Any partial frame was a runt so go back to start */
if (gsm->state != GSM_START) {
- gsm->malformed++;
+ if (gsm->state != GSM_SEARCH)
+ gsm->malformed++;
gsm->state = GSM_START;
}
/* A SOF in GSM_START means we are still reading idling or