On Fri, Aug 26, 2022 at 4:44 AM Christian Brauner <brauner@xxxxxxxxxx> wrote: > On Fri, Aug 19, 2022 at 02:50:57PM -0400, Paul Moore wrote: > > On Tue, Aug 16, 2022 at 6:12 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote: > > > On Fri, Jul 8, 2022 at 5:35 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote: > > > > > > > > Since userfaultfd doesn't implement a write operation, it is more > > > > appropriate to open it read-only. > > > > > > > > When userfaultfds are opened read-write like it is now, and such fd is > > > > passed from one process to another, SELinux will check both read and > > > > write permissions for the target process, even though it can't actually > > > > do any write operation on the fd later. > > > > > > > > Inspired by the following bug report, which has hit the SELinux scenario > > > > described above: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1974559 > > > > > > > > Reported-by: Robert O'Callahan <roc@xxxxxxxxxxxxx> > > > > Fixes: 86039bd3b4e6 ("userfaultfd: add new syscall to provide memory externalization") > > > > Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx> > > > > --- > > > > > > > > Resending as the last submission was ignored for over a year... > > > > > > > > https://lore.kernel.org/lkml/20210624152515.1844133-1-omosnace@xxxxxxxxxx/T/ > > > > > > > > I marked this as RFC, because I'm not sure if this has any unwanted side > > > > effects. I only ran this patch through selinux-testsuite, which has a > > > > simple userfaultfd subtest, and a reproducer from the Bugzilla report. > > > > > > > > Please tell me whether this makes sense and/or if it passes any > > > > userfaultfd tests you guys might have. > > > > > > > > fs/userfaultfd.c | 4 ++-- > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > VFS folks, any objection to this patch? It seems reasonable to me and > > > I'd really prefer this to go in via the vfs tree, but I'm not above > > > merging this via the lsm/next tree to get someone in vfs land to pay > > > attention to this ... > > > > Okay, final warning, if I don't see any objections to this when I make > > my patch sweep next week I'm going to go ahead and merge this via the > > LSM tree. > > Makes sense, > Acked-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> Merged into lsm/next, thanks all. -- paul-moore.com
