Messages in this thread | | | Date | Wed, 24 Nov 2021 11:33:11 -0600 | From | "Serge E. Hallyn" <> | Subject | Re: [PATCH 5.10 130/154] block: Check ADMIN before NICE for IOPRIO_CLASS_RT |
| |
On Wed, Nov 24, 2021 at 04:31:22PM +0100, Greg Kroah-Hartman wrote: > On Wed, Nov 24, 2021 at 04:22:50PM +0200, Jari Ruusu wrote: > > Greg Kroah-Hartman wrote: > > > From: Alistair Delva <adelva@google.com> > > > > > > commit 94c4b4fd25e6c3763941bdec3ad54f2204afa992 upstream. > > [SNIP] > > > --- a/block/ioprio.c > > > +++ b/block/ioprio.c > > > @@ -69,7 +69,14 @@ int ioprio_check_cap(int ioprio) > > > > > > switch (class) { > > > case IOPRIO_CLASS_RT: > > > - if (!capable(CAP_SYS_NICE) && !capable(CAP_SYS_ADMIN)) > > > + /* > > > + * Originally this only checked for CAP_SYS_ADMIN, > > > + * which was implicitly allowed for pid 0 by security > > > + * modules such as SELinux. Make sure we check > > > + * CAP_SYS_ADMIN first to avoid a denial/avc for > > > + * possibly missing CAP_SYS_NICE permission. > > > + */ > > > + if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE)) > > > return -EPERM; > > > fallthrough; > > > /* rt has prio field too */ > > > > What exactly is above patch trying to fix? > > It does not change control flow at all, and added comment is misleading. > > See the thread on the mailing list for what it does and why it is > needed. > > It does change the result when selinux is enabled. > > thanks, > > greg k-h
The case where we create a newer more fine grained capability which is a sub-cap of a broader capability like CAP_SYS_ADMIN is analogous. See check_syslog_permissions() for instance.
So I think a helper like
int capable_either_or(int cap1, int cap2) { if (has_capability_noaudit(current, cap1)) return 0; return capable(cap2); }
might be worthwhile.
| |