On 07/11/2016 08:51 PM, YongQin Liu wrote:
> 
> 
> On 11 July 2016 at 23:08, Stephen Smalley <[email protected]
> <mailto:[email protected]>> wrote:
> 
>     On 07/07/2016 01:11 PM, YongQin Liu wrote:
>     > Hi, ALL
>     >
>     > When I try AOSP master with the hikey board, I see following sys_module
>     > denial on netd domain.
>     >
>     >     avc: denied { sys_module } for pid=1775 comm="netd" capability=16
>     >     scontext=u:r:netd:s0 tcontext=u:r:netd:s0 tclass=capability 
> permissive=0
>     >
>     >
>     > After some check, I found it was caused by "capable(CAP_SYS_MODULE)"
>     > call in dev_load method of the kernel net/core/dev_ioctl.c file here:
>     >
>     > 
> https://android.googlesource.com/kernel/hikey-linaro/+/refs/heads/android-hikey-linaro-4.4/net/core/dev_ioctl.c#371
>     >
>     >
>     > When I comment the capable(CAP_SYS_MODULE) check, there is no
>     >  sys_module denial output.
>     >
>     > I did not dig into the implementation of capable, but should not it just
>     > return false without the sys_module denial?
> 
>     Why would you expect it to do that?  netd has CAP_SYS_MODULE in its
>     effective capability set, so you'll pass the capability module check but
>     will then fail the SELinux check if it is not allowed by policy.
> 
> When it fail the SELinux check, it will output the avc denial like this:
>>     avc: denied { sys_module } for pid=1775 comm="netd" capability=16
>>     scontext=u:r:netd:s0 tcontext=u:r:netd:s0 tclass=capability
> permissive=0
> 
> And this will make people to think why this avc denial is caused, and
> will check if there is something wrong in the source.
> 
> So I think it's better to not show this avc denial during the check when
> CAP_SYS_MODULE is not allowed.

Then add a dontaudit rule for it.



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