From: Anant Thazhemadam anant.thazhemadam@gmail.com
[ Upstream commit c8c958a58fc67f353289986850a0edf553435702 ]
In can_rcv(), cfd->len is uninitialized when skb->len = 0, and this uninitialized cfd->len is accessed nonetheless by pr_warn_once().
Fix this uninitialized variable access by checking cfd->len's validity condition (cfd->len > CAN_MAX_DLEN) separately after the skb->len's condition is checked, and appropriately modify the log messages that are generated as well. In case either of the required conditions fail, the skb is freed and NET_RX_DROP is returned, same as before.
Fixes: 8cb68751c115 ("can: af_can: can_rcv(): replace WARN_ONCE by pr_warn_once") Reported-by: syzbot+9bcb0c9409066696d3aa@syzkaller.appspotmail.com Tested-by: Anant Thazhemadam anant.thazhemadam@gmail.com Signed-off-by: Anant Thazhemadam anant.thazhemadam@gmail.com Link: https://lore.kernel.org/r/20201103213906.24219-2-anant.thazhemadam@gmail.com Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- net/can/af_can.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/net/can/af_can.c b/net/can/af_can.c index 04132b0b5d360..1201846dc07e3 100644 --- a/net/can/af_can.c +++ b/net/can/af_can.c @@ -722,16 +722,25 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev, { struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
- if (unlikely(dev->type != ARPHRD_CAN || skb->len != CAN_MTU || - cfd->len > CAN_MAX_DLEN)) { - pr_warn_once("PF_CAN: dropped non conform CAN skbuf: dev type %d, len %d, datalen %d\n", + if (unlikely(dev->type != ARPHRD_CAN || skb->len != CAN_MTU)) { + pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d\n", + dev->type, skb->len); + goto free_skb; + } + + /* This check is made separately since cfd->len would be uninitialized if skb->len = 0. */ + if (unlikely(cfd->len > CAN_MAX_DLEN)) { + pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d, datalen %d\n", dev->type, skb->len, cfd->len); - kfree_skb(skb); - return NET_RX_DROP; + goto free_skb; }
can_receive(skb, dev); return NET_RX_SUCCESS; + +free_skb: + kfree_skb(skb); + return NET_RX_DROP; }
static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,