linux-kernel - Re: [PATCH 1/1] aio: make sure the input "timeout" value is valid

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Date:   Mon, 26 Mar 2018 21:43:03 -0700
From:   Deepa Dinamani <deepa.kernel@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Jeff Moyer <jmoyer@...hat.com>,
        "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Benjamin LaHaise <bcrl@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-aio <linux-aio@...ck.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Tianhong Ding <dingtianhong@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Libin <huawei.libin@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH 1/1] aio: make sure the input "timeout" value is valid

On Mon, Mar 26, 2018 at 2:55 PM, Matthew Wilcox <willy@...radead.org> wrote:
> On Mon, Mar 26, 2018 at 10:01:30PM +0200, Arnd Bergmann wrote:
>> I had suggested a more complete helper function at some point,
>> to take care of all combinations of checking/non-checking, 32/64
>> bit, microsecond/nanosecond, and zeroing/checking the upper 32 bits
>> of nanoseconds before comparing against 1 billion, but Deepa
>> thought that was overkill, so I didn't continue that.
>
> Yeah, that sounds like a nightmare to use ;-)
>
>> For all I can tell, the get_timespec64() helper should almost always
>> include the check, the one exception I know is utimensat() and related
>> functions that may encode the special UTIME_NOW and UTIME_OMIT
>> constants in the nanoseconds.
>
> So do you endorse the get_valid_timespec64() patch I posted up-thread?
> We can't just make get_timespec64 return an errno directly because it'll
> require changing all the users.

I missed this thread earlier.

I had leaned away from this idea before, because of the special cases
which don't need it. I was also trying to keep the syntax close to
copy_from_user(), which is what was there before.

We could probably just change all the
get_timespec64()/compat_get_timespec64() to do the check using a
simple coccinelle script.
I can own this.

But, this would not be needed if Arnd is posting the other helper function.
Arnd, let me know what you prefer here.

-Deepa