On 10/12/2016 11:51 AM, Roberts, William C wrote:
> If Bin is using our N tree, then all the stuff for debugfs are exact
> matches:
> 
>  
> 
> /sys/kernel/debug/sync      u:object_r:debugfs_graphics_sync:s0
> 
> /sys/kernel/debug/dri/0/i915_frequency_info u:object_r:debugfs_graphics:s0
> 
> /sys/kernel/debug/pstate_snb/setpoint u:object_r:debugfs_pstate:s0
> 
>  
> 
> Bin, can you confirm the state of your tree? You can run this command to
> find the entries:
> 
>  
> 
> find . -name file_contexts | xargs grep 'kernel/debug'

It could be any /sys entry that breaks the partial match pruning logic
(by enabling a possible match of any subdir), not just ones under
/sys/kernel/debug.

> 
>  
> 
> Thanks,
> 
> Bill
> 
>  
> 
>  
> 
> *From:*Nick Kralevich [mailto:[email protected]]
> *Sent:* Wednesday, October 12, 2016 11:42 AM
> *To:* Roberts, William C <[email protected]>
> *Cc:* Stephen Smalley <[email protected]>; [email protected];
> Yang, Bin Y <[email protected]>
> *Subject:* Re: labelling /sys/kernel/debug aka debugfs
> 
>  
> 
> Can you attach the file_contexts file you're using? Or at least all the
> entries starting with /sys? In the past, when I've seen this kind of
> slow restorecon on boot, it's been due to a regex which defeats the
> restorecon directory tree walking optimizations.
> 
>  
> 
> -- Nick
> 
>  
> 
> On Wed, Oct 12, 2016 at 6:42 AM, Roberts, William C
> <[email protected] <mailto:[email protected]>> wrote:
> 
> 
> 
>     > -----Original Message-----
>     > From: Stephen Smalley [mailto:[email protected]
>     <mailto:[email protected]>]
>     > Sent: Wednesday, October 12, 2016 9:37 AM
>     > To: Roberts, William C <[email protected]
>     <mailto:[email protected]>>; 'seandroid-
>     > [email protected] <mailto:[email protected]>'
>     <[email protected] <mailto:[email protected]>>
>     > Cc: Yang, Bin Y <[email protected] <mailto:[email protected]>>
>     > Subject: Re: labelling /sys/kernel/debug aka debugfs
>     >
>     > On 10/12/2016 09:24 AM, Roberts, William C wrote:
>     > > It’s been reported that labelling via restorecon_recursive
>     > > /sys/kernel/debug is taking 0.25s on a device. I wanted to verify a
>     > > thought:
>     > >
>     > >
>     > >
>     > > It looks like genfscon per file labeling is supported by selinux
>     (like
>     > > procfs), on linux master branch, I see:
>     > >
>     > >
>     > >
>     > > selinux_set_mnt_opts():
>     > >
>     > > <snip>
>     > >
>     > > 815         if (!strcmp(sb->s_type->name, "debugfs") ||
>     > >
>     > > 816             !strcmp(sb->s_type->name, "sysfs") ||
>     > >
>     > > 817             !strcmp(sb->s_type->name, "pstore"))
>     > >
>     > > 818                 sbsec->flags |= SE_SBGENFS;
>     > >
>     > > <snip>
>     > >
>     > >
>     > >
>     > > Would using genfscon statements and removing the
>     restorecon_recursive
>     > > be faster since it avoids the tree walk? Any caveats, issues one
>     can think of?
>     >
>     > First, I'd be interested in understanding why that is taking so
>     long, and compare
>     > with time on restorecon_recursive /sys (performed directly by init).
>     >
>     > The SE for Android todo list does suggest investigating this for
>     replacing the
>     > restorecon_recursive /sys, so it would make sense to investigate
>     it for both.  It
>     > does require that the device kernel include the necessary support.
>     As noted in
>     > https://android-review.googlesource.com/#/c/151776/, you are also
>     limited in
>     > that genfscon only supports pathname prefix matching, not regexes.
> 
>     I don't see any uses where the lack of regex support would be a problem.
>     I'll see if Bin, the reporter, can collect more stats for us, Yang
>     could you collect
>     those?
> 
> 
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> 
> 
> 
>  
> 
> -- 
> 
> Nick Kralevich | Android Security | [email protected]
> <mailto:[email protected]> | 650.214.4037
> 
> 
> 
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