linux-kernel - Re: [PATCH] time: Validate the usec before covert to nsec in do

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Message-ID: <2c4e8e8d-6e90-0d09-cf28-45330eb598ce@huawei.com>
Date:   Mon, 8 Jul 2019 18:42:13 +0800
From:   "zhangxiaoxu (A)" <zhangxiaoxu5@...wei.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     <john.stultz@...aro.org>, <sboyd@...nel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] time: Validate the usec before covert to nsec in
 do_adjtimex



在 2019/7/8 17:24, Thomas Gleixner 写道:
> On Mon, 8 Jul 2019, ZhangXiaoxu wrote:
> 
>> When covert the usec to nsec, it will multiple 1000, it maybe
>> overflow and lead an undefined behavior.
>>
>> For example, users may input an negative tv_usec values when
>> call adjtimex syscall, then multiple 1000 maybe overflow it
>> to a positive and legal number.
>>
>> So, we should validate the usec before coverted it to nsec.
> 
> That's correct, but the actuall inject function wants to keep the sanity
> check,
timekeeping_inject_offset is called only by timekeeping_warp_clock and do_adjtimex.
The do_adjtimex already validate it, and timekeeping_warp_clock is set tv_nsec=0.
We keep the sanity check is for some other maybe use this function?
I had send a v2 to keep the sanity check in timekeeping_inject_offset.

Thanks.
> 
> Thanks,
> 
> 	tglx
> 
> .
>