On 05/11/2015 04:52 PM, Stephen Smalley wrote: > 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... > The patch solves the problem. Thanks. I would say that a system with /etc/selinux/config with SELINUXTYPE=targeted and without targeted policy is misconfigured. A problem could with an empty config file but it's probably a minor corner case. Petr -- Petr Lautrbach
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