On Wed, Feb 23, 2022 at 7:43 AM Richard Haines <richard_c_haines@xxxxxxxxxxxxxx> wrote: > On Wed, 2022-02-23 at 13:12 +0100, Ondrej Mosnacek wrote: > > 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? > > What about FS_IOC_GETFLAGS Unless I'm mistaken, FIGETBSZ should be largely fs independent. > > > > > 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. > > Okay will use Paul's. Thanks guys. -- paul-moore.com
