linux-kernel - Re: [git pull] vfs.git pile 11

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Message-ID: <20170706202927.GX10672@ZenIV.linux.org.uk>
Date:   Thu, 6 Jul 2017 21:29:27 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Kees Cook <keescook@...omium.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [git pull] vfs.git pile 11

On Thu, Jul 06, 2017 at 09:18:26PM +0100, Al Viro wrote:
> On Thu, Jul 06, 2017 at 12:45:36PM -0700, Kees Cook wrote:
> > 
> > +   if (unlikely(!check_copy_size(addr, bytes, false)))
> > +       return false;
> > +   else
> > +       return _copy_from_iter_full(addr, bytes, i);
> > 
> > Can these be rewritten to avoid the double-negative?
> 
> Matter of taste - I've no strong preferences here.
> 
> > +   might_fault();
> > 
> > Should this be might_sleep()? Just from reading the patch it looked
> > like you were adding might_sleep()s in the other cases.
> 
> D'oh - shouldn't have written that pull request message before the
> first cup of coffee...  might_sleep() it is, of course.

Hrm...  Said that, might_sleep() doesn't check one thing might_fault()
does - the
#if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
        if (current->mm)
                might_lock_read(&current->mm->mmap_sem);
#endif
thing.  Let me think a bit...