Re: [Bug #11500] /proc/net bug related to selinux

[Stephen Smalley]

On Sat, 2008-09-13 at 12:37 -0700, Andrew Morton wrote:
> On Sat, 13 Sep 2008 10:15:43 +1000 (EST) James Morris <jmorris@xxxxxxxxx> wrote:
> 
> > On Fri, 12 Sep 2008, Andrew Morton wrote:
> > 
> > > > > Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=11500
> > > > > Subject		: /proc/net bug related to selinux
> > > > > Submitter	: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > > > Date		: 2008-09-04 17:45 (9 days old)
> > > > > References	: http://marc.info/?l=linux-kernel&m=122055041313270&w=4
> > > > 
> > > > I think this might be a regression caused by namespace changes which we 
> > 
> > By which I mean, this was caused by a non-SELinux change to the upstream 
> > kernel many, many eons ago.
> 
> hm, seems that 2.6.24 is OK but 2.6.25 is not.  I must have missed the
> bug when testing 2.6.25-based kernels.
> 
> I started a git bisection search but after half an hour I hit bad
> bisection breakage: a complete machine hang in fib_rules_init().
> 
> > > > addressed in SELinux policy.  Which distro version & policy version is 
> > > > this seen with?
> > > > 
> > > 
> > > FC5 on x86_32 and FC6 on x86_64.
> > 
> > As mentioned in the bugzilla, any related avc messages would be useful.
> 
> 2.6.25 dmesg: http://userweb.kernel.org/~akpm/dmesg-sony.txt
> /var/log/messages: http://userweb.kernel.org/~akpm/messages-sony.txt
> 
> The latter includes this:
> 
> Sep 13 12:32:43 sony kernel: SELinux:  class key not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  class dccp_socket not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  class memprotect not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  class peer not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  class capability2 not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission open in class dir not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission open in class file not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission open in class chr_file not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission open in class blk_file not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission open in class fifo_file not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission dccp_recv in class node not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission dccp_send in class node not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission recvfrom in class node not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission sendto in class node not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission dccp_recv in class netif not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission dccp_send in class netif not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission ingress in class netif not defined in policy
> Sep 13 12:32:43 sony kernel: SELinux:  permission egress in class netif not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission setkeycreate in class process not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission setsockcreate in class process not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission setfcap in class capability not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission polmatch in class association not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission flow_in in class packet not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission flow_out in class packet not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission forward_in in class packet not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux:  permission forward_out in class packet not defined in policy
> Sep 13 12:32:44 sony kernel: SELinux: the above unknown classes and permissions will be denied
> Sep 13 12:32:44 sony kernel: type=1403 audit(1221309118.644:3): policy loaded auid=4294967295 ses=4294967295
> Sep 13 12:32:44 sony kernel: type=1400 audit(1221334321.726:4): avc:  denied  { audit_write } for  pid=400 comm="hwclock" capability=29 scontext=system_u:system_r:hwclock_t:s0 tcontext=system_u:system_r:hwclock_t:s0 tclass=capability
> 
> 
> Why am I seeing this on two machines and two vanilla-installed distros
> but nobody else is reporting it?

What we actually need to see is the output of:
/sbin/ausearch -i -m AVC -sv no

However, the most likely explanation is simply that when /proc/net was
changed from being a directory to being a symlink to /proc/self/net,
that introduced an additional permission check on accesses
of /proc/net/<whatever>, namely the read check on the symlink itself.
And since that check wasn't happening on /proc/net accesses with older
kernels, older policies didn't allow it.

As to why others haven't reported it, I expect that they have updated
their policies to newer ones that allow the necessary access.  The fact
that legacy distros wouldn't have such updated policies isn't surprising
- they don't push updates to those distros for new kernels.  FC5 and FC6
are both EOL'd, right?

In any event, we didn't change anything in SELinux - the change was
elsewhere (in the proc/net implementation).  Don't blame the messenger
please.

-- 
Stephen Smalley
National Security Agency

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