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: [email protected]
Tested-by: Anant Thazhemadam <[email protected]>
Signed-off-by: Anant Thazhemadam <[email protected]>
---
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
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: [email protected]
> Tested-by: Anant Thazhemadam <[email protected]>
> Signed-off-by: Anant Thazhemadam <[email protected]>
> ---
> 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()"?
> {
> 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.
> + 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 () {"
> + 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
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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: [email protected]
>> Tested-by: Anant Thazhemadam <[email protected]>
>> Signed-off-by: Anant Thazhemadam <[email protected]>
>> ---
>> 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
On 11/2/20 8:44 AM, Anant Thazhemadam wrote:
>
> 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: [email protected]
>>> Tested-by: Anant Thazhemadam <[email protected]>
>>> Signed-off-by: Anant Thazhemadam <[email protected]>
>>> ---
>>> 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)?
Please make it two patches. Please add a "Fixes" line to both patches.
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |