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 :) > 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? -- paul-moore.com
