diff mbox series

[5.15,068/102] tty: n_gsm: fix buffer over-read in gsm_dlci_data()

Message ID 20220516193625.949023655@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH May 16, 2022, 7:36 p.m. UTC 
From: Daniel Starke <daniel.starke@siemens.com>

commit fd442e5ba30aaa75ea47b32149e7a3110dc20a46 upstream.

'len' is decreased after each octet that has its EA bit set to 0, which
means that the value is encoded with additional octets. However, the final
octet does not decreases 'len' which results in 'len' being one byte too
long. A buffer over-read may occur in tty_insert_flip_string() as it tries
to read one byte more than the passed content size of 'data'.
Decrease 'len' also for the final octet which has the EA bit set to 1 to
write the correct number of bytes from the internal receive buffer to the
virtual tty.

Fixes: 2e124b4a390c ("TTY: switch tty_flip_buffer_push")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220504081733.3494-1-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_gsm.c |    1 +
 1 file changed, 1 insertion(+)
diff mbox series

Patch

--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1587,6 +1587,7 @@  static void gsm_dlci_data(struct gsm_dlc
 			if (len == 0)
 				return;
 		}
+		len--;
 		slen++;
 		tty = tty_port_tty_get(port);
 		if (tty) {