From 4b4359122a414cc15156e13e3805988b71ff9da0 Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Mon, 6 Jun 2022 06:17:25 +0000 Subject: [PATCH 1/2] xen/arm: p2m: Prevent adding mapping when domain is dying During the domain destroy process, the domain will still be accessible until it is fully destroyed. So does the P2M because we don't bail out early if is_dying is non-zero. If a domain has permission to modify the other domain's P2M (i.e. dom0, or a stubdomain), then foreign mapping can be added past relinquish_p2m_mapping(). Therefore, we need to prevent mapping to be added when the domain is dying. This commit prevents such adding of mapping by adding the d->is_dying check to p2m_set_entry(). Also this commit enhances the check in relinquish_p2m_mapping() to make sure that no mappings can be added in the P2M after the P2M lock is released. This is part of CVE-2022-33746 / XSA-410. Signed-off-by: Julien Grall Signed-off-by: Henry Wang Tested-by: Henry Wang Reviewed-by: Stefano Stabellini --- xen/arch/arm/p2m.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c index fb71fa4c1c90..cbeff90f4371 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -1093,6 +1093,15 @@ int p2m_set_entry(struct p2m_domain *p2m, { int rc = 0; + /* + * Any reference taken by the P2M mappings (e.g. foreign mapping) will + * be dropped in relinquish_p2m_mapping(). As the P2M will still + * be accessible after, we need to prevent mapping to be added when the + * domain is dying. + */ + if ( unlikely(p2m->domain->is_dying) ) + return -ENOMEM; + while ( nr ) { unsigned long mask; @@ -1610,6 +1619,8 @@ int relinquish_p2m_mapping(struct domain *d) unsigned int order; gfn_t start, end; + BUG_ON(!d->is_dying); + /* No mappings can be added in the P2M after the P2M lock is released. */ p2m_write_lock(p2m); start = p2m->lowest_mapped_gfn; -- 2.37.1