On 02-11-2020 12:40, Marc Kleine-Budde wrote: > On 11/2/20 4:13 AM, Anant Thazhemadam wrote: >> 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+9bcb0c9409066696d3aa@xxxxxxxxxxxxxxxxxxxxxxxxx >> Tested-by: Anant Thazhemadam <anant.thazhemadam@xxxxxxxxx> >> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@xxxxxxxxx> >> --- >> 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, > Can you create a similar patch for "can_rcv()"? Yes, I can. Would it be alright if that was part of the v2 itself (since it's similar changes)? Or would I have to split them up into 2 different patches and send it as a 2-patch series (since the changes made are in different functions)? > >> { >> 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. > Please don't use C++ comment style in the kernel. Noted. I'll have this fixed in the v2. > >> + else if (unlikely(cfd->len > CANFD_MAX_DLEN)) { > Please move the "else" right after the closing curly bracket: "} else if () {" > or convert it into an "if () {" Noted. > >> + 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 */ >> > regards, > Marc Thank you for your time. Thanks, Anant