tty: n_gsm: fix malformed counter for out of frame data

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>

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index bee92cd3f90a5711145d105f69dfc80eaa5b2df3..cbeb8907a6cffc1342d20ba0b506cda5ef51101d 100644 (file)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1973,7 +1973,8 @@ static void gsm1_receive(struct gsm_mux *gsm, unsigned char c)
                }
                /* 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