GPF when doing jail -r, possibly an use-after-free

[Mikolaj Golub]

On Mon, 9 Jul 2012 06:07:05 +0000 Bjoern A. Zeeb wrote:

 BAZ> On 9. Jul 2012, at 06:01 , Mikolaj Golub wrote:

 >> 
 >> On Sun, 8 Jul 2012 20:52:55 +0000 Bjoern A. Zeeb wrote:
 >> 
 >> BAZ> Situation 1)
 >> 
 >> BAZ>         epairNa is in base, eiparNb is jail foo
 >> BAZ>         stop jail foo: jail -r foo
 >> BAZ>         both epairN[ab] will live in base and can be destiryed without vnet switching
 >> 
 >> BAZ> Situation 2)
 >> 
 >> BAZ>         epairNa is in base, eiparNb is jail foo
 >> BAZ>         you are in jail foo and type epairNb destroy;  that should not be allowed
 >> 
 >> BAZ> Situation 3)
 >> 
 >> BAZ>         epairNa is in base, eiparNb is jail foo
 >> BAZ>         you are in base and type ifconfig epairNa destroy
 >> 
 >> BAZ>         This is your case ...  I am not sure what I'd expect in this case,
 >> BAZ>         especailly given epair is special...  You probably are right.
 >> BAZ>         Ideally I'd not allow it to be destroyed unless both are in the
 >> BAZ>         if_home_vnet.  However it seems we allow this; so in that case
 >> BAZ>         I definitively make sure to use the CURVNET_SET_QUIET() version
 >> BAZ>         to avoid the expected noise otherwise.
 >> 
 >> It looks like epair was expected to allow this, because in non-patched version
 >> it already did switching before freeing the interface. It just did not switch
 >> bere detaching.
 >> 
 >> CURVNET_SET_QUIET() is used in the current version of the patch so I suppose I
 >> can commit it.
 >> 
 >> But if you think that just not allowing to destroy unless both ends are in the
 >> f_home_vnet is a preferred solution and it is not late to change this I can
 >> provide the patch.

 BAZ> Get it in for now; it helps people.  We should keep the other things in mind and
 BAZ> write down a proper policy; it's more interesting as you can do other things with
 BAZ> cloners you can create inside a vnet as well, today and later.

Thank you for the discussion. The patch is committed.

-- 
Mikolaj Golub