Messages in this thread | | | Date | Tue, 4 Mar 2008 20:24:03 +0200 | Subject | Re: [PATCH BUGFIX -rc3] Smack: Don't register smackfs if we're not loaded | From | "Ahmed S. Darwish" <> |
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Hi Linus,
[Adding SELinux devs to CC list, please follow to the SELinux point.]
On Tue, Mar 04, 2008 at 09:21:19AM -0800, Linus Torvalds wrote: > > > On Tue, 4 Mar 2008, Ahmed S. Darwish wrote: > > > > Smackfs initialization without an enabled Smack leads to > > an early Oops that renders the system unusable. > > I really think this is bogus. Global enables like this are just wrong, and > a sign that something else bad is going on. > > What is the oops? Why does it happen? >
The problem occurs when Smack is built-in the kernel but not chosen to register itself on boot. Smack was not chosen on boot cause either security=AnotherLSM or security=NonExistentLSM.
In all cases, init_smk_fs() ,which registers smackfs, got called cause it's an __initcall(init_smack_fs). This include the cases where smack __was not__ chosen on boot.
Making smackfs mountable when Smack is not registered leads to:
1- an Oops by dereferncing the NULL security pointer: current->security (*)
2- Smackfs code got executed though naturally all the code assumes that smack is already registered with the security system leading to several problems.
3- The bogus idea of having a subsystem interface available when the subsystem itself is not available!
So the global is used in init_smk_fs to not register smackfs if Smack wasn't enabled on boot.
---- SELinux:
I think the SELinux folks faced the same problem too. In my first local iteration of the security= parameter patch, I forgot to set `selinux_disable = 1' if SELinux wasn't chosen on boot.
This led to dozen of SELinux Udev events and also led to selinuxfs being available even though SELinux hooks _weren't_ registered.
Regards,
(*) Could not save the oops cause it occured too early, but it was like this:
__init_call init_smk_fs(void) smk_unlbl_ambient(NULL) /* * Here: current->security = NULL, cause SMACK initial setup * was not executed. */ smack_to_secid(current->security) strncmp(.., current->security, ..) --
"Better to light a candle, than curse the darkness"
Ahmed S. Darwish Homepage: http://darwish.07.googlepages.com Blog: http://darwish-07.blogspot.com
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