[PATCH 1/2] xen/cpupool: Reject attempts to add a domain to CPUPOOLID_NONE

[Andrew Cooper <andrew.cooper3@citrix.com>]

c/s cfc52148444f ("xen/domain: Reduce the quantity of initialisation for
system domains") removed the path in domain_create() which called
sched_init_domain() with CPUPOOLID_NONE for system domains.

Arguably, that changeset should have cleaned up this path too.

However, c/s 92ea9c54fc81 ("arm/dom0less: assign dom0less guests to cpupools")
changed domain_create() from using a hardcoded poolid of 0, to using a value
passed by the toolstack.

While CPUPOOLID_NONE is an internal constant, userspace can pass -1 for the
cpupool_id parameter and attempt to construct a real domain using default ops,
which at a minimum will fail the assertion in dom_scheduler().

Fixes: 92ea9c54fc81 ("arm/dom0less: assign dom0less guests to cpupools")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Juergen Gross <jgross@suse.com>
CC: Dario Faggioli <dfaggioli@suse.com>
CC: Luca Fancellu <luca.fancellu@arm.com>
---
 xen/common/sched/cpupool.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index f6e3d97e5288..f1aa2db5f463 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -619,8 +619,6 @@ int cpupool_add_domain(struct domain *d, unsigned int poolid)
     int rc;
     int n_dom = 0;
 
-    if ( poolid == CPUPOOLID_NONE )
-        return 0;
     spin_lock(&cpupool_lock);
     c = cpupool_find_by_id(poolid);
     if ( c == NULL )
-- 
2.11.0