6.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
commit b19ab7ee2c4c1ec5f27c18413c3ab63907f7d55c upstream.
When lookahead has "consumed" some characters (la_count > 0),
n_tty_receive_buf_standard() and n_tty_receive_buf_closing() for
characters beyond the la_count are given wrong cp/fp offsets which
leads to duplicating and losing some characters.
If la_count > 0, correct buffer pointers and make count consistent too
(the latter is not strictly necessary to fix the issue but seems more
logical to adjust all variables immediately to keep state consistent).
Reported-by: Vadym Krevs <vkrevs@xxxxxxxxx>
Fixes: 6bb6fa6908eb ("tty: Implement lookahead to process XON/XOFF timely")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218834
Tested-by: Vadym Krevs <vkrevs@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240514140429.12087-1-ilpo.jarvinen@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/n_tty.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1619,15 +1619,25 @@ static void __receive_buf(struct tty_str
else if (ldata->raw || (L_EXTPROC(tty) && !preops))
n_tty_receive_buf_raw(tty, cp, fp, count);
else if (tty->closing && !L_EXTPROC(tty)) {
- if (la_count > 0)
+ if (la_count > 0) {
n_tty_receive_buf_closing(tty, cp, fp, la_count, true);
- if (count > la_count)
- n_tty_receive_buf_closing(tty, cp, fp, count - la_count, false);
+ cp += la_count;
+ if (fp)
+ fp += la_count;
+ count -= la_count;
+ }
+ if (count > 0)
+ n_tty_receive_buf_closing(tty, cp, fp, count, false);
} else {
- if (la_count > 0)
+ if (la_count > 0) {
n_tty_receive_buf_standard(tty, cp, fp, la_count, true);
- if (count > la_count)
- n_tty_receive_buf_standard(tty, cp, fp, count - la_count, false);
+ cp += la_count;
+ if (fp)
+ fp += la_count;
+ count -= la_count;
+ }
+ if (count > 0)
+ n_tty_receive_buf_standard(tty, cp, fp, count, false);
flush_echoes(tty);
if (tty->ops->flush_chars)
