In canfd_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 > CANFD_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.
Reported-by: syzbot+9bcb0c9409066696d...@syzkaller.appspotmail.com
Tested-by: Anant Thazhemadam <anant.thazhema...@gmail.com>
Signed-off-by: Anant Thazhemadam <anant.thazhema...@gmail.com>
---
This patch was locally tested using the reproducer and .config file
generated by syzbot.
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 ea29a6d97ef5..1b9f2e50f065 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -694,16 +694,25 @@ static int canfd_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 != CANFD_MTU ||
- cfd->len > CANFD_MAX_DLEN)) {
- pr_warn_once("PF_CAN: dropped non conform CAN FD skbuf: dev
type %d, len %d, datalen %d\n",
+ if (unlikely(dev->type != ARPHRD_CAN || skb->len != CANFD_MTU)) {
+ pr_warn_once("PF_CAN: dropped non conform CAN FD 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.
+ else if (unlikely(cfd->len > CANFD_MAX_DLEN)) {
+ pr_warn_once("PF_CAN: dropped non conform CAN FD 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;
}
/* af_can protocol functions */
--
2.25.1
