On 2020-01-26, Aleksa Sarai <cyphar@xxxxxxxxxx> wrote:
> On 2020-01-24, Sargun Dhillon <sargun@xxxxxxxxx> wrote:
> > static long seccomp_notify_recv(struct seccomp_filter *filter,
> > void __user *buf)
> > {
> > struct seccomp_knotif *knotif = NULL, *cur;
> > struct seccomp_notif unotif;
> > + struct task_struct *group_leader;
> > + bool send_pidfd;
> > ssize_t ret;
> >
> > + if (copy_from_user(&unotif, buf, sizeof(unotif)))
> > + return -EFAULT;
> > /* Verify that we're not given garbage to keep struct extensible. */
> > - ret = check_zeroed_user(buf, sizeof(unotif));
> > - if (ret < 0)
> > - return ret;
> > - if (!ret)
> > + if (unotif.id ||
> > + unotif.pid ||
> > + memchr_inv(&unotif.data, 0, sizeof(unotif.data)) ||
> > + unotif.pidfd)
> > + return -EINVAL;
>
> IMHO this check is more confusing than the original check_zeroed_user().
> Something like the following is simpler and less prone to forgetting to
> add a new field in the future:
>
> if (memchr_inv(&unotif, 0, sizeof(unotif)))
> return -EINVAL;
Also the check in the patch doesn't ensure that any unnamed padding is
zeroed -- memchr_inv(&unotif, 0, sizeof(unotif)) does.
--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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