netdev - Re: [PATCH v2] can: bcm: check timer values before ktime conversion

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Date:   Thu, 17 Jan 2019 17:04:28 +0100
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     Andre Naujoks <nautsch2@...il.com>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-can@...r.kernel.org,
        lifeasageek@...il.com, threeearcat@...il.com,
        syzkaller@...glegroups.com, Kyungtae Kim <kt0755@...il.com>,
        linux-stable <stable@...r.kernel.org>
Subject: Re: [PATCH v2] can: bcm: check timer values before ktime conversion

Hello Marc,

I would like to provide a stable patch for pre-4.18 kernels and need a 
commit hash as reference.

Would you like to take that patch into upstream?

Best regards,
Oliver

On 1/16/19 2:31 PM, Andre Naujoks wrote:
> Am 13.01.19 um 19:31 schrieb Oliver Hartkopp:
>> Kyungtae Kim detected a potential integer overflow in bcm_[rx|tx]_setup()
>> when the conversion into ktime multiplies the given value with NSEC_PER_USEC
>> (1000).
>>
>> Reference: https://marc.info/?l=linux-can&m=154732118819828&w=2
>>
>> Add a check for the given tv_usec, so that the value stays below one second.
>> Additionally limit the tv_sec value to a reasonable value for CAN related
>> use-cases of 400 days and ensure all values to be positive.
>>
>> Reported-by: Kyungtae Kim <kt0755@...il.com>
>> Tested-by: Oliver Hartkopp <socketcan@...tkopp.net>
>> Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
>> Cc: linux-stable <stable@...r.kernel.org> # >= 2.6.26
> 
> Acked-by: Andre Naujoks <nautsch2@...il.com>
> 
> Sorry for the late reply, but I seem to have missed the initial send of
> v2 of this. I wanted to at least ack it, since I made such a fuss about
> the timeouts. :-)
> 
> Regards
>    Andre
> 
>> ---
>>   net/can/bcm.c | 27 +++++++++++++++++++++++++++
>>   1 file changed, 27 insertions(+)
>>
>> diff --git a/net/can/bcm.c b/net/can/bcm.c
>> index 0af8f0db892a..d4ae0a1471f3 100644
>> --- a/net/can/bcm.c
>> +++ b/net/can/bcm.c
>> @@ -67,6 +67,9 @@
>>    */
>>   #define MAX_NFRAMES 256
>>   
>> +/* limit timers to 400 days for sending/timeouts */
>> +#define BCM_TIMER_SEC_MAX (400*24*60*60)
>> +
>>   /* use of last_frames[index].flags */
>>   #define RX_RECV    0x40 /* received data for this element */
>>   #define RX_THR     0x80 /* element not been sent due to throttle feature */
>> @@ -140,6 +143,22 @@ static inline ktime_t bcm_timeval_to_ktime(struct bcm_timeval tv)
>>   	return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC);
>>   }
>>   
>> +/* check limitations for timeval provided by user */
>> +static int bcm_is_invalid_tv(struct bcm_msg_head *msg_head)
>> +{
>> +	if ((msg_head->ival1.tv_sec < 0) ||
>> +	    (msg_head->ival1.tv_sec > BCM_TIMER_SEC_MAX) ||
>> +	    (msg_head->ival1.tv_usec < 0) ||
>> +	    (msg_head->ival1.tv_usec >= USEC_PER_SEC) ||
>> +	    (msg_head->ival2.tv_sec < 0) ||
>> +	    (msg_head->ival2.tv_sec > BCM_TIMER_SEC_MAX) ||
>> +	    (msg_head->ival2.tv_usec < 0) ||
>> +	    (msg_head->ival2.tv_usec >= USEC_PER_SEC))
>> +		return 1;
>> +
>> +	return 0;
>> +}
>> +
>>   #define CFSIZ(flags) ((flags & CAN_FD_FRAME) ? CANFD_MTU : CAN_MTU)
>>   #define OPSIZ sizeof(struct bcm_op)
>>   #define MHSIZ sizeof(struct bcm_msg_head)
>> @@ -873,6 +892,10 @@ static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
>>   	if (msg_head->nframes < 1 || msg_head->nframes > MAX_NFRAMES)
>>   		return -EINVAL;
>>   
>> +	/* check timeval limitations */
>> +	if ((msg_head->flags & SETTIMER) && bcm_is_invalid_tv(msg_head))
>> +		return -EINVAL;
>> +
>>   	/* check the given can_id */
>>   	op = bcm_find_op(&bo->tx_ops, msg_head, ifindex);
>>   	if (op) {
>> @@ -1053,6 +1076,10 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
>>   	     (!(msg_head->can_id & CAN_RTR_FLAG))))
>>   		return -EINVAL;
>>   
>> +	/* check timeval limitations */
>> +	if ((msg_head->flags & SETTIMER) && bcm_is_invalid_tv(msg_head))
>> +		return -EINVAL;
>> +
>>   	/* check the given can_id */
>>   	op = bcm_find_op(&bo->rx_ops, msg_head, ifindex);
>>   	if (op) {
>>
>