x86/mm: Refactor map_pages_to_xen to have only a single exit path

We will soon need to perform clean-ups before returning.

No functional change.

This is part of XSA-345.

Reported-by: Hongyan Xia <hongyxia@amazon.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
master commit: 08e6c6f80b018878476adc2c4e5679d2ce5cb4b1
master date: 2020-10-20 14:19:31 +0200

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index fd734ff94772b5911956bca07f8e5f6deb0d1806..f6df0a41f18b6c17243a04dd97254211b67a0311 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5112,6 +5112,7 @@ int map_pages_to_xen(
     l2_pgentry_t *pl2e, ol2e;
     l1_pgentry_t *pl1e, ol1e;
     unsigned int  i;
+    int rc = -ENOMEM;
 
 #define flush_flags(oldf) do {                 \
     unsigned int o_ = (oldf);                  \
@@ -5132,7 +5133,8 @@ int map_pages_to_xen(
         l3_pgentry_t ol3e, *pl3e = virt_to_xen_l3e(virt);
 
         if ( !pl3e )
-            return -ENOMEM;
+            goto out;
+
         ol3e = *pl3e;
 
         if ( cpu_has_page1gb &&
@@ -5218,7 +5220,7 @@ int map_pages_to_xen(
 
             pl2e = alloc_xen_pagetable();
             if ( pl2e == NULL )
-                return -ENOMEM;
+                goto out;
 
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                 l2e_write(pl2e + i,
@@ -5247,7 +5249,7 @@ int map_pages_to_xen(
 
         pl2e = virt_to_xen_l2e(virt);
         if ( !pl2e )
-            return -ENOMEM;
+            goto out;
 
         if ( ((((virt >> PAGE_SHIFT) | mfn) &
                ((1u << PAGETABLE_ORDER) - 1)) == 0) &&
@@ -5289,7 +5291,7 @@ int map_pages_to_xen(
             {
                 pl1e = virt_to_xen_l1e(virt);
                 if ( pl1e == NULL )
-                    return -ENOMEM;
+                    goto out;
             }
             else if ( l2e_get_flags(*pl2e) & _PAGE_PSE )
             {
@@ -5315,7 +5317,7 @@ int map_pages_to_xen(
 
                 pl1e = alloc_xen_pagetable();
                 if ( pl1e == NULL )
-                    return -ENOMEM;
+                    goto out;
 
                 for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
                     l1e_write(&pl1e[i],
@@ -5458,7 +5460,10 @@ int map_pages_to_xen(
 
 #undef flush_flags
 
-    return 0;
+    rc = 0;
+
+ out:
+    return rc;
 }
 
 int populate_pt_range(unsigned long virt, unsigned long mfn,