From 7a7406ba1d8912719eb7c9eec2d7cd34f49dfac0 Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Tue, 11 Oct 2022 15:32:58 +0200 Subject: [PATCH] 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 master commit: 3ebe773293e3b945460a3d6f54f3b91915397bab master date: 2022-10-11 14:20:18 +0200 --- 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 2290b7114f..35943589fc 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -1085,6 +1085,15 @@ 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; @@ -1579,6 +1588,8 @@ 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; -- 2.39.5