From 1237659523813696af4083279a7b871d407cbd48 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Wed, 8 Aug 2018 15:54:30 +0100 Subject: [PATCH] common/gnttab: Explicitly default to gnttab v1 during domain creation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit For reasons which appear to be exclusively down to poor review of the grant table v2 code, a grant table's version field was wasn't initialised during creation. A number of problems (including XSAs) have occurred in the past trying trying to use a grant table which hasn't been properly set up, and various areas of the code cope with v0 by defaulting to v1. In particular, the toolstack using GNTTABOP_setup_table to be able to fill in the store/console grants has a side effect of switching to v1. In hindsight however, this "fixup if we see 0" is a very poor, with a substantial degree of risk. Explicitly default to grant table v1 during domain create, and let the rest of the code work safely in the knowledge that the version is sensibly set. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich Reviewed-by: Roger Pau Monné --- xen/common/grant_table.c | 39 ++++++++------------------------------- 1 file changed, 8 insertions(+), 31 deletions(-) diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c index d9ec711c73..009b1e2626 100644 --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -50,8 +50,8 @@ struct grant_table { /* Lock protecting the maptrack limit */ spinlock_t maptrack_lock; /* - * The defined versions are 1 and 2. Set to 0 if we don't know - * what version to use yet. + * Defaults to v1. May be changed with GNTTABOP_set_version. All other + * values are invalid. */ unsigned int gt_version; /* Resource limits of the domain. */ @@ -222,7 +222,6 @@ nr_maptrack_frames(struct grant_table *t) static grant_entry_header_t * shared_entry_header(struct grant_table *t, grant_ref_t ref) { - ASSERT(t->gt_version != 0); if ( t->gt_version == 1 ) return (grant_entry_header_t*)&shared_entry_v1(t, ref); else @@ -1302,20 +1301,6 @@ unmap_common( grant_read_lock(rgt); - if ( rgt->gt_version == 0 ) - { - /* - * This ought to be impossible, as such a mapping should not have - * been established (see the nr_grant_entries(rgt) bounds check in - * gnttab_map_grant_ref()). Doing this check only in - * gnttab_unmap_common_complete() - as it used to be done - would, - * however, be too late. - */ - rc = GNTST_bad_gntref; - flags = 0; - goto unlock_out; - } - op->rd = rd; op->ref = map->ref; @@ -1932,9 +1917,6 @@ gnttab_setup_table( goto unlock; } - if ( gt->gt_version == 0 ) - gt->gt_version = 1; - if ( (op.nr_frames > nr_grant_frames(gt) || ((gt->gt_version > 1) && (grant_to_status_frames(op.nr_frames) > nr_status_frames(gt)))) && @@ -2991,15 +2973,11 @@ gnttab_set_version(XEN_GUEST_HANDLE_PARAM(gnttab_set_version_t) uop) switch ( gt->gt_version ) { - case 0: - if ( op.version == 2 ) - { case 1: - /* XXX: We could maybe shrink the active grant table here. */ - res = gnttab_populate_status_frames(currd, gt, nr_grant_frames(gt)); - if ( res < 0) - goto out_unlock; - } + /* XXX: We could maybe shrink the active grant table here. */ + res = gnttab_populate_status_frames(currd, gt, nr_grant_frames(gt)); + if ( res < 0) + goto out_unlock; break; case 2: for ( i = 0; i < GNTTAB_NR_RESERVED_ENTRIES; i++ ) @@ -3594,6 +3572,8 @@ grant_table_create( percpu_rwlock_resource_init(&t->lock, grant_rwlock); spin_lock_init(&t->maptrack_lock); + t->gt_version = 1; + /* Okay, install the structure. */ t->domain = d; d->grant_table = t; @@ -3869,9 +3849,6 @@ int gnttab_map_frame(struct domain *d, unsigned long idx, gfn_t gfn, grant_write_lock(gt); - if ( gt->gt_version == 0 ) - gt->gt_version = 1; - if ( gt->gt_version == 2 && (idx & XENMAPIDX_grant_table_status) ) { -- 2.30.2