On Wed, Feb 23, 2022 at 12:58 PM Richard Haines <richard_c_haines@xxxxxxxxxxxxxx> wrote: > On Tue, 2022-02-22 at 18:28 -0500, Paul Moore wrote: > > On Mon, Feb 21, 2022 at 8:15 AM Richard Haines > > <richard_c_haines@xxxxxxxxxxxxxx> wrote: > > > > > > These ioctls are equivalent to fcntl(fd, F_SETFD, flags), which > > > SELinux > > > always allows too. Furthermore, a failed FIOCLEX could result in a > > > file > > > descriptor being leaked to a process that should not have access to > > > it. > > > > > > As this patch removes access controls, a policy capability needs to > > > be > > > enabled in policy to always allow these ioctls. > > > > > > Based-on-patch-by: Demi Marie Obenour <demiobenour@xxxxxxxxx> > > > Signed-off-by: Richard Haines <richard_c_haines@xxxxxxxxxxxxxx> > > > --- > > > V2 Change: Control via a policy capability. See this thread for > > > discussion: > > > https://lore.kernel.org/selinux/CAHC9VhQEPxYP_KU56gAGNHKQaxucY8gSsHiUB42PVgADBAccRQ@xxxxxxxxxxxxxx/T/#t > > > > > > With this patch and the polcap enabled, the selinux-testsuite will > > > fail: > > > ioctl/test at line 47 - Will need a fix. > > > > > > security/selinux/hooks.c | 7 +++++++ > > > security/selinux/include/policycap.h | 1 + > > > security/selinux/include/policycap_names.h | 3 ++- > > > security/selinux/include/security.h | 7 +++++++ > > > 4 files changed, 17 insertions(+), 1 deletion(-) > > > > Thanks Richard for putting together the v2 of this patch. > > > > As far as the test is concerned, it seems like the quick-n-dirty fix > > is to simply remove the ioctl(FIOCLEX) test in test_noioctl.c; is > > everyone okay with that? At least that is what I'm going to do with > > my local copy that I use to validate the kernel-secnext builds unless > > someone has a better patch :) > > To fix this I was planning to submit a patch that would change the > ioctl(FIOCLEX) tests to ioctl(FS_IOC_GETFSLABEL) as that would continue > to test the xperms. That one seems to be implemented only by some filesystems. Is there any more generic one we could use? > > > > > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > > > index 5b6895e4f..030c41652 100644 > > > --- a/security/selinux/hooks.c > > > +++ b/security/selinux/hooks.c > > > @@ -3745,6 +3745,13 @@ static int selinux_file_ioctl(struct file > > > *file, unsigned int cmd, > > > CAP_OPT_NONE, true); > > > break; > > > > > > + case FIOCLEX: > > > + case FIONCLEX: > > > + /* Must always succeed if polcap set, else default: > > > */ > > > + if (selinux_policycap_ioctl_skip_cloexec()) > > > + break; > > > + fallthrough; > > > + > > > > The break/fallthrough looks like it might be a little more fragile > > than necessary, how about something like this: > > > > case FIOCLEX: > > case FIONCLEX: > > if (!selinux_policycap_ioctl_skip_cloexec()) > > error = ioctl_has_perm(cred, file, FILE__IOCTL, (u16) cmd); > > break; > > > > Yes, it does duplicate the default ioctl_has_perm() call, but since > > we > > are effectively deprecating this and locking the FIOCLEX/FIONCLEX > > behavior with this policy capability it seems okay to me (and > > preferable to relying on the fallthrough). > > > > Thoughts? > > Yes I did ponder this and in my first attempt I had this before the > switch(): > > /* Must always succeed if polcap set */ > if (selinux_policycap_ioctl_skip_cloexec() && > (cmd == FIOCLEX || cmd == FIONCLEX)) > return 0; > > switch (cmd) { > case FIONREAD: > case FIBMAP: > > but changed to within the switch(), anyway I'm happy to resubmit a > patch either way. I agree with Paul's suggestion. Better to duplicate the simple call than to complicate the code flow. -- Ondrej Mosnacek Software Engineer, Linux Security - SELinux kernel Red Hat, Inc.
