This is a note to let you know that I've just added the patch titled
tty: n_gsm: fix possible out-of-bounds in gsm0_receive()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tty-n_gsm-fix-possible-out-of-bounds-in-gsm0_receive.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 47388e807f85948eefc403a8a5fdc5b406a65d5a Mon Sep 17 00:00:00 2001
From: Daniel Starke <daniel.starke@xxxxxxxxxxx>
Date: Wed, 24 Apr 2024 07:48:41 +0200
Subject: tty: n_gsm: fix possible out-of-bounds in gsm0_receive()
From: Daniel Starke <daniel.starke@xxxxxxxxxxx>
commit 47388e807f85948eefc403a8a5fdc5b406a65d5a upstream.
Assuming the following:
- side A configures the n_gsm in basic option mode
- side B sends the header of a basic option mode frame with data length 1
- side A switches to advanced option mode
- side B sends 2 data bytes which exceeds gsm->len
Reason: gsm->len is not used in advanced option mode.
- side A switches to basic option mode
- side B keeps sending until gsm0_receive() writes past gsm->buf
Reason: Neither gsm->state nor gsm->len have been reset after
reconfiguration.
Fix this by changing gsm->count to gsm->len comparison from equal to less
than. Also add upper limit checks against the constant MAX_MRU in
gsm0_receive() and gsm1_receive() to harden against memory corruption of
gsm->len and gsm->mru.
All other checks remain as we still need to limit the data according to the
user configuration and actual payload size.
Reported-by: j51569436@xxxxxxxxx
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218708
Tested-by: j51569436@xxxxxxxxx
Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240424054842.7741-1-daniel.starke@xxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/n_gsm.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1972,8 +1972,12 @@ static void gsm0_receive(struct gsm_mux
break;
case GSM_DATA: /* Data */
gsm->buf[gsm->count++] = c;
- if (gsm->count == gsm->len)
+ if (gsm->count >= MAX_MRU) {
+ gsm->bad_size++;
+ gsm->state = GSM_SEARCH;
+ } else if (gsm->count >= gsm->len) {
gsm->state = GSM_FCS;
+ }
break;
case GSM_FCS: /* FCS follows the packet */
gsm->received_fcs = c;
@@ -2053,7 +2057,7 @@ static void gsm1_receive(struct gsm_mux
gsm->state = GSM_DATA;
break;
case GSM_DATA: /* Data */
- if (gsm->count > gsm->mru) { /* Allow one for the FCS */
+ if (gsm->count > gsm->mru || gsm->count > MAX_MRU) { /* Allow one for the FCS */
gsm->state = GSM_OVERRUN;
gsm->bad_size++;
} else
Patches currently in stable-queue which might be from daniel.starke@xxxxxxxxxxx are
queue-4.19/tty-n_gsm-fix-possible-out-of-bounds-in-gsm0_receive.patch
