[PATCH] Skip damage calls if DamageCreate fails in exa functions

[Alan Coopersmith]

Fixes parfait errors such as:
   Null pointer dereference (CWE 476): Write to null pointer pDamage
        at line 1833 of miext/damage/damage.c in function 'DamageRegister'.
          Function DamageCreate may return constant 'NULL' at line 1775,
              called at line 232 of exa/exa_migration_mixed.c
              in function 'exaPrepareAccessReg_mixed'.
          Constant 'NULL' passed into function DamageRegister,
              argument pDamage, from call at line 237.
          Null pointer introduced at line 1775 of miext/damage/damage.c
              in function 'DamageCreate'.
   Null pointer dereference (CWE 476): Write to null pointer pDamage
        at line 1833 of miext/damage/damage.c in function 'DamageRegister'.
          Function DamageCreate may return constant 'NULL' at line 1775,
              called at line 104 of exa/exa_mixed.c
              in function 'exaCreatePixmap_mixed'.
          Constant 'NULL' passed into function DamageRegister,
              argument pDamage, from call at line 109.
          Null pointer introduced at line 1775 of miext/damage/damage.c
              in function 'DamageCreate'.

Checks are similar to handling results of other calls to DamageCreate.

[ This bug was found by the Parfait 1.3.0 bug checking tool.
  http://labs.oracle.com/pls/apex/f?p=labs:49:::::P49_PROJECT_ID:13 ]

Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
---
 exa/exa_migration_mixed.c |   11 +++++++----
 exa/exa_mixed.c           |   11 +++++++----
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/exa/exa_migration_mixed.c b/exa/exa_migration_mixed.c
index 445c4fc..5519dc1 100644
--- a/exa/exa_migration_mixed.c
+++ b/exa/exa_migration_mixed.c
@@ -234,10 +234,13 @@ exaPrepareAccessReg_mixed(PixmapPtr pPixmap, int index, RegionPtr pReg)
                                                pPixmap->drawable.pScreen,
                                                pPixmap);
 
-            DamageRegister(&pPixmap->drawable, pExaPixmap->pDamage);
-            /* This ensures that pending damage reflects the current operation. */
-            /* This is used by exa to optimize migration. */
-            DamageSetReportAfterOp(pExaPixmap->pDamage, TRUE);
+            if (pExaPixmap->pDamage) {
+                DamageRegister(&pPixmap->drawable, pExaPixmap->pDamage);
+                /* This ensures that pending damage reflects the current
+                 * operation. This is used by exa to optimize migration.
+                 */
+                DamageSetReportAfterOp(pExaPixmap->pDamage, TRUE);
+            }
 
             if (has_gpu_copy) {
                 exaPixmapDirty(pPixmap, 0, 0, pPixmap->drawable.width,
diff --git a/exa/exa_mixed.c b/exa/exa_mixed.c
index 0fb4091..1ffb1a5 100644
--- a/exa/exa_mixed.c
+++ b/exa/exa_mixed.c
@@ -106,10 +106,13 @@ exaCreatePixmap_mixed(ScreenPtr pScreen, int w, int h, int depth,
                                                pPixmap->drawable.pScreen,
                                                pPixmap);
 
-            DamageRegister(&pPixmap->drawable, pExaPixmap->pDamage);
-            /* This ensures that pending damage reflects the current operation. */
-            /* This is used by exa to optimize migration. */
-            DamageSetReportAfterOp(pExaPixmap->pDamage, TRUE);
+            if (pExaPixmap->pDamage) {
+                DamageRegister(&pPixmap->drawable, pExaPixmap->pDamage);
+                /* This ensures that pending damage reflects the current
+                 * operation. This is used by exa to optimize migration.
+                 */
+                DamageSetReportAfterOp(pExaPixmap->pDamage, TRUE);
+            }
         }
     }
 
-- 
1.7.9.2