diff options
| author | Daniel Starke <daniel.starke@siemens.com> | 2024-04-24 07:48:41 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-06-16 13:23:23 +0200 |
| commit | 9513d4148950b05bc99fa7314dc883cc0e1605e5 (patch) | |
| tree | cdfe72682e13e61b70abdb01c8e3fc7f7351e35d | |
| parent | 911d38be151921a5d152bb55e81fd752384c6830 (diff) | |
tty: n_gsm: fix possible out-of-bounds in gsm0_receive()
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@gmail.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218708
Tested-by: j51569436@gmail.com
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/20240424054842.7741-1-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/n_gsm.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index a38539fd8253..59a2ede0ece2 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1972,8 +1972,12 @@ static void gsm0_receive(struct gsm_mux *gsm, unsigned char c) 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, unsigned char c) 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 |