linux-kernel - Re: [PATCH 32/32] aio: implement io

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Message-ID: <x49k1wg1tp9.fsf@segfault.boston.devel.redhat.com>
Date:   Wed, 17 Jan 2018 08:49:22 -0500
From:   Jeff Moyer <jmoyer@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Al Viro <viro@...IV.linux.org.uk>, Avi Kivity <avi@...lladb.com>,
        linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
        netdev@...r.kernel.org, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 32/32] aio: implement io_pgetevents

Christoph Hellwig <hch@....de> writes:

> On Wed, Jan 17, 2018 at 04:27:21AM +0000, Al Viro wrote:
>> On Tue, Jan 16, 2018 at 07:41:24PM -0500, Jeff Moyer wrote:
>> >  	if (sigmask) {
>> > -		if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
>> > +		if (!access_ok(VERIFY_READ, sigmask,
>> > +			       sizeof(void *) + sizeof(size_t)) ||
>> > +		    __get_user(up, (sigset_t __user * __user *)sigmask) ||
>> > +		    __get_user(sigsetsize,
>> > +			       (size_t __user *)(sigmask + sizeof(void *))))
>> >  			return -EFAULT;
>> 
>> How about copy_from_user() on a struct?  Making eyes bleed is fun, but
>> people tend to get annoyed when you do it to them...
>
> Above is the copy & paste version from pselect.  I've got both copy_from_user
> and that horrible version in my tree, and if we really need this awfull
> calling convention copy_from_user certainly is much better.  pselect
> also should be switched to explicit struct + copy_from_user while
> we're at it.  In fact glibc defines a struct for the userland version
> to start with.

Yeah, I did both, but stuck with this variant as that's what pselect
did.  I'm fine with switching to the struct variant.

-Jeff