Messages in this thread | | | Date | Mon, 28 Jan 2019 08:58:17 +0100 | From | Peter Zijlstra <> | Subject | Re: [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.
| |