lkml.org 
[lkml]   [2019]   [Jan]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [tip:sched/core] sched/core: Fix a potential double-fetch bug in sched_copy_attr()
On Sun, Jan 27, 2019 at 12:04:44PM +0100, Thomas Gleixner wrote:
> On Mon, 21 Jan 2019, tip-bot for Kangjie Lu wrote:
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index a674c7db2f29..d4d3514c4fe9 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -4499,6 +4499,9 @@ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *a
> > if (ret)
> > return -EFAULT;
> >
> > + /* In case attr->size was changed by user-space: */
> > + attr->size = size;
> > +
>
> Just when pondering to send that to Linus, I tried to write up a concise
> summary for this which made me look at the patch.
>
> If the size changed, then its clear that user space fiddled with the date
> between the size fetch and the full copy from user. So why restoring the
> size instead of doing the obvious:
>
> if (attr->size != size)
> return -ECRAP;
>
> Hmm?

Sure; but if we do that we should also change perf_copy_attr() which has
the exact same thing.

\
 
 \ /
  Last update: 2019-01-28 08:58    [W:0.077 / U:1.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site