CVE-2014-8106: cirrus: fix blit region check

Backport of qemu-upstream:
 * bf25983345ca44aec3dd92c57142be45452bd38a
 * d3532a0db02296e687711b8cdc7791924efccea0

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/hw/cirrus_vga.c b/hw/cirrus_vga.c
index 11ce212d4846f9bf81a49c3e385f0dc2291efdd1..d3bf4cff518ae817b5c534b23e5a54f86de17831 100644 (file)
--- a/hw/cirrus_vga.c
+++ b/hw/cirrus_vga.c
@@ -34,6 +34,8 @@
 #include "qemu-xen.h"
 #include "qemu-log.h"
 
+#include <assert.h>
+
 /*
  * TODO:
  *    - destination write mask support not complete (bits 5..7)
@@ -223,20 +225,6 @@
 
 #define ABS(a) ((signed)(a) > 0 ? a : -a)
 
-#define BLTUNSAFE(s) \
-    ( \
-        ( /* check dst is within bounds */ \
-            (s)->cirrus_blt_height * ABS((s)->cirrus_blt_dstpitch) \
-                + ((s)->cirrus_blt_dstaddr & (s)->cirrus_addr_mask) > \
-                    (s)->vram_size \
-        ) || \
-        ( /* check src is within bounds */ \
-            (s)->cirrus_blt_height * ABS((s)->cirrus_blt_srcpitch) \
-                + ((s)->cirrus_blt_srcaddr & (s)->cirrus_addr_mask) > \
-                    (s)->vram_size \
-        ) \
-    )
-
 struct CirrusVGAState;
 typedef void (*cirrus_bitblt_rop_t) (struct CirrusVGAState *s,
                                      uint8_t * dst, const uint8_t * src,
@@ -315,6 +303,50 @@ static void cirrus_vga_mem_writew(void *opaque, target_phys_addr_t addr, uint32_
  *
  ***************************************/
 
+static bool blit_region_is_unsafe(struct CirrusVGAState *s,
+                                  int32_t pitch, int32_t addr)
+{
+    if (pitch < 0) {
+        int64_t min = addr
+            + ((int64_t)s->cirrus_blt_height-1) * pitch;
+        int32_t max = addr
+            + s->cirrus_blt_width;
+        if (min < 0 || max >= s->vram_size) {
+            return true;
+        }
+    } else {
+        int64_t max = addr
+            + ((int64_t)s->cirrus_blt_height-1) * pitch
+            + s->cirrus_blt_width;
+        if (max >= s->vram_size) {
+            return true;
+        }
+    }
+    return false;
+}
+
+static bool blit_is_unsafe(struct CirrusVGAState *s)
+{
+    /* should be the case, see cirrus_bitblt_start */
+    assert(s->cirrus_blt_width > 0);
+    assert(s->cirrus_blt_height > 0);
+
+    if (s->cirrus_blt_width > CIRRUS_BLTBUFSIZE) {
+        return true;
+    }
+
+    if (blit_region_is_unsafe(s, s->cirrus_blt_dstpitch,
+                              s->cirrus_blt_dstaddr & s->cirrus_addr_mask)) {
+        return true;
+    }
+    if (blit_region_is_unsafe(s, s->cirrus_blt_srcpitch,
+                              s->cirrus_blt_srcaddr & s->cirrus_addr_mask)) {
+        return true;
+    }
+
+    return false;
+}
+
 static void cirrus_bitblt_rop_nop(CirrusVGAState *s,
                                   uint8_t *dst,const uint8_t *src,
                                   int dstpitch,int srcpitch,
@@ -676,7 +708,7 @@ static int cirrus_bitblt_common_patterncopy(CirrusVGAState * s,
 
     dst = s->vram_ptr + (s->cirrus_blt_dstaddr & s->cirrus_addr_mask);
 
-    if (BLTUNSAFE(s))
+    if (blit_is_unsafe(s))
         return 0;
 
     (*s->cirrus_rop) (s, dst, src,
@@ -694,7 +726,7 @@ static int cirrus_bitblt_solidfill(CirrusVGAState *s, int blt_rop)
 {
     cirrus_fill_t rop_func;
 
-    if (BLTUNSAFE(s))
+    if (blit_is_unsafe(s))
         return 0;
     rop_func = cirrus_fill[rop_to_index[blt_rop]][s->cirrus_blt_pixelwidth - 1];
     rop_func(s, s->vram_ptr + (s->cirrus_blt_dstaddr & s->cirrus_addr_mask),
@@ -790,7 +822,7 @@ static void cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
 
 static int cirrus_bitblt_videotovideo_copy(CirrusVGAState * s)
 {
-    if (BLTUNSAFE(s))
+    if (blit_is_unsafe(s))
         return 0;
 
     cirrus_do_copy(s, s->cirrus_blt_dstaddr - s->start_addr,