From: Oleksij Rempel o.rempel@pengutronix.de

The current stack implementation do not support ECTS requests of not aligned TP sized blocks.

If ECTS will request a block with size and offset spanning two TP blocks, this will cause memcpy() to read beyond the queued skb (which does only contain one TP sized block).

Sometimes KASAN will detect this read if the memory region beyond the skb was previously allocated and freed. In other situations it will stay undetected. The ETP transfer in any case will be corrupted.

This patch adds a sanity check to avoid this kind of read and abort the session with error J1939_XTP_ABORT_ECTS_TOO_BIG.

Reported-by: syzbot+5322482fe520b02aea30@syzkaller.appspotmail.com Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") Cc: linux-stable stable@vger.kernel.org # >= v5.4 Signed-off-by: Oleksij Rempel o.rempel@pengutronix.de Link: https://lore.kernel.org/r/20200807105200.26441-3-o.rempel@pengutronix.de Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de --- net/can/j1939/transport.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)

diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index b135c5e2a86e..30957c9a8eb7 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -787,6 +787,18 @@ static int j1939_session_tx_dat(struct j1939_session *session) if (len > 7) len = 7;

+ if (offset + len > se_skb->len) { + netdev_err_once(priv->ndev, + "%s: 0x%p: requested data outside of queued buffer: offset %i, len %i, pkt.tx: %i\n", + __func__, session, skcb->offset, se_skb->len , session->pkt.tx); + return -EOVERFLOW; + } + + if (!len) { + ret = -ENOBUFS; + break; + } + memcpy(&dat[1], &tpdat[offset], len); ret = j1939_tp_tx_dat(session, dat, len + 1); if (ret < 0) { @@ -1120,6 +1132,9 @@ static enum hrtimer_restart j1939_tp_txtimer(struct hrtimer *hrtimer) * cleanup including propagation of the error to user space. */ break; + case -EOVERFLOW: + j1939_session_cancel(session, J1939_XTP_ABORT_ECTS_TOO_BIG); + break; case 0: session->tx_retry = 0; break;