On 05/11/2015 10:11 AM, Petr Lautrbach wrote: > On 05/11/2015 04:04 PM, Stephen Smalley wrote: >> On 05/11/2015 10:02 AM, Stephen Smalley wrote: >>> On 05/11/2015 09:49 AM, Petr Lautrbach wrote: >>>> On 05/11/2015 03:43 PM, Stephen Smalley wrote: >>>>> On 05/11/2015 09:40 AM, Petr Lautrbach wrote: >>>>>> On 04/17/2015 03:42 PM, Stephen Smalley wrote: >>>>>>> SELinux can be disabled via the selinux=0 kernel parameter or via >>>>>>> /sys/fs/selinux/disable (triggered by setting SELINUX=disabled in >>>>>>> /etc/selinux/config). In either case, selinuxfs will be unmounted >>>>>>> and unregistered and therefore it is sufficient to check for the >>>>>>> selinuxfs mount. We do not need to check for no-policy-loaded and >>>>>>> treat that as SELinux-disabled anymore; that is a relic of Fedora Core 2 >>>>>>> days. Drop the no-policy-loaded test, which was a bit of a hack anyway >>>>>>> (checking whether getcon_raw() returned "kernel" as that can only happen >>>>>>> if no policy is yet loaded and therefore security_sid_to_context() only >>>>>>> has the initial SID name available to return as the context). >>>>>>> >>>>>>> May possibly fix https://bugzilla.redhat.com/show_bug.cgi?id=1195074 >>>>>>> by virtue of removing the call to getcon_raw() and therefore avoiding >>>>>>> use of tls on is_selinux_enabled() calls. Regardless, it will make >>>>>>> is_selinux_enabled() faster and simpler. >>>>>>> >>>>>> >>>>>> This patch breaks system with SELinux enabled kernel and without >>>>>> loaded/installed an SELinux policy, see [1]. >>>>>> >>>>>> Would it be feasible to have is_selinux_enabled() connected to existence >>>>>> of SELINUX variable in /etc/selinux/config file for the cases when >>>>>> there's no specific kernel command line option used in running system? >>>>>> Or would it break something else? >>>>>> >>>>>> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1219045 >>>>> >>>>> Sorry, does this occur even if they have SELINUX=disabled in >>>>> /etc/selinux/config? >>>> >>>> It works with SELINUX=disabled. It's only related to systems without >>>> /etc/selinux/config and without selinux=0 on kernel command line. >>> >>> I see. So I can see that it is a regression for such systems, but such >>> systems are definitely running suboptimally by NOT disabling SELinux if >>> they are not going to even load a policy. They are just wasting all of >>> the SELinux hook call overhead in the kernel. > > I agree. > >>> >>> In any event, one of the benefits of the change that caused this >>> regression is that it makes is_selinux_enabled() very fast and avoids >>> any need to open any extra files on calls to it, thereby improving >>> performance on both SELinux-enabled and SELinux-disabled systems. >>> >>> I don't think we need or want to actually have it read >>> /etc/selinux/config and look for a SELINUX= variable. Isn't it >>> sufficient to test for the existence of an /etc/selinux/config file, >>> e.g. access("/etc/selinux/config", F_OK)? > > I'm fine with that. > >>> >>> We'll have to wrap that test with #ifndef ANDROID as Android does not >>> use /etc/selinux/config. >> >> Oh, and let's do it once in init_selinuxmnt() and cache the result so we >> aren't calling access() on each is_selinux_enabled() call. > > Do you want me to prepare and send a patch? See if my patch solves the problem. I do however see one other potential scenario that could occur in Fedora, i.e. where they have selinux-policy installed (and thus have an /etc/selinux/config) but do not have selinux-policy-targeted installed (and thus do not have any /etc/selinux/targeted). Not sure how far down this path we should travel... _______________________________________________ Selinux mailing list Selinux@xxxxxxxxxxxxx To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx.
