linux-kernel - Re: [PATCH] time: verify time values in adjtimex ADJ

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Date:	Sat, 5 Dec 2015 19:15:41 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	john.stultz@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] time: verify time values in adjtimex ADJ_SETOFFSET to
 avoid overflow

On 12/05/2015 12:10 PM, Thomas Gleixner wrote:
> On Thu, 3 Dec 2015, Sasha Levin wrote:
> 
>> Make sure the tv_usec makes sense. We might multiply them later which can
>> cause an overflow and undefined behavior.
>>
>> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
>> ---
>>  kernel/time/timekeeping.c |    4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
>> index d563c19..aa3c1c2 100644
>> --- a/kernel/time/timekeeping.c
>> +++ b/kernel/time/timekeeping.c
>> @@ -1987,6 +1987,10 @@ int do_adjtimex(struct timex *txc)
>>  
>>  	if (txc->modes & ADJ_SETOFFSET) {
>>  		struct timespec delta;
>> +
>> +		if (txc->time.tv_usec >= USEC_PER_SEC || txc->time.tv_usec <= -USEC_PER_SEC)
>> +			return -EINVAL;
> 
> That's not a canonical timeval. timeval_valid() is what you want to
> check it. Or has adjtimex some magic exception here?

Nope, it looks like timeval_valid() is indeed what I've needed to use.

Is there a reason ntp_validate_timex() doesn't do timeval_valid() too
for at least the ADJ_SETOFFSET case? If not, I'll add it in.


Thanks,
Sasha
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