[Xen-changelog] [xen staging] xen/x86: hap: Clean-up and harden hap_enable()

[patchbot@xxxxxxx]

commit a47ae19672fce8e377277f23336692f9eab4fca1
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Mon Feb 3 23:57:05 2020 +0000
Commit:     Julien Grall <julien@xxxxxxx>
CommitDate: Thu Mar 5 12:59:46 2020 +0000

    xen/x86: hap: Clean-up and harden hap_enable()
    
    Unlike shadow_enable(), hap_enable() can only be called once during
    domain creation and with the mode equal to
    PG_external | PG_translate | PG_refcounts.
    
    If it were called twice, then we might have some interesting problems
    as the p2m tables would be re-allocated (and therefore all the mappings
    would be lost).
    
    Add code to sanity check the mode and that the function is only called
    once. Take the opportunity to an if checking that PG_translate is set.
    
    Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/mm/hap/hap.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index 31362a31b6..510776112c 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -445,6 +445,13 @@ int hap_enable(struct domain *d, u32 mode)
     unsigned int i;
     int rv = 0;
 
+    if ( mode != (PG_external | PG_translate | PG_refcounts) )
+        return -EINVAL;
+
+    /* The function can only be called once per domain. */
+    if ( d->arch.paging.mode != 0 )
+        return -EEXIST;
+
     domain_pause(d);
 
     old_pages = d->arch.paging.hap.total_pages;
@@ -465,13 +472,10 @@ int hap_enable(struct domain *d, u32 mode)
     d->arch.paging.alloc_page = hap_alloc_p2m_page;
     d->arch.paging.free_page = hap_free_p2m_page;
 
-    /* allocate P2m table */
-    if ( mode & PG_translate )
-    {
-        rv = p2m_alloc_table(p2m_get_hostp2m(d));
-        if ( rv != 0 )
-            goto out;
-    }
+    /* allocate P2M table */
+    rv = p2m_alloc_table(p2m_get_hostp2m(d));
+    if ( rv != 0 )
+        goto out;
 
     for ( i = 0; i < MAX_NESTEDP2M; i++ )
     {
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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