cirrus: multiple bugfixes, including CVE-2017-2615 fix.

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Merge remote-tracking branch 'remotes/kraxel/tags/pull-vga-20170202-2' into staging

cirrus: multiple bugfixes, including CVE-2017-2615 fix.

# gpg: Signature made Thu 02 Feb 2017 15:03:35 GMT
# gpg:                using RSA key 0x4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/pull-vga-20170202-2:
  cirrus: fix oob access issue (CVE-2017-2615)
  cirrus: fix blit address mask handling
  cirrus: allow zero source pitch in pattern fill rops
  cirrus: handle negative pitch in cirrus_invalidate_region()

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/display/cirrus_vga.c

@@ -272,15 +272,11 @@ static void cirrus_update_memory_access(CirrusVGAState *s);
 static bool blit_region_is_unsafe(struct CirrusVGAState *s,
                                   int32_t pitch, int32_t addr)
 {
-    if (!pitch) {
-        return true;
-    }
     if (pitch < 0) {
         int64_t min = addr
-            + ((int64_t)s->cirrus_blt_height-1) * pitch;
+            + ((int64_t)s->cirrus_blt_height - 1) * pitch
-        int32_t max = addr
+            - s->cirrus_blt_width;
-            + s->cirrus_blt_width;
+        if (min < -1 || addr >= s->vga.vram_size) {
-        if (min < 0 || max > s->vga.vram_size) {
             return true;
         }
     } else {
@@ -294,8 +290,11 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s,
     return false;
 }
 
-static bool blit_is_unsafe(struct CirrusVGAState *s, bool dst_only)
+static bool blit_is_unsafe(struct CirrusVGAState *s, bool dst_only,
+                           bool zero_src_pitch_ok)
 {
+    int32_t check_pitch;
+
     /* should be the case, see cirrus_bitblt_start */
     assert(s->cirrus_blt_width > 0);
     assert(s->cirrus_blt_height > 0);
@@ -304,15 +303,25 @@ static bool blit_is_unsafe(struct CirrusVGAState *s, bool dst_only)
         return true;
     }
 
+    if (!s->cirrus_blt_dstpitch) {
+        return true;
+    }
+
     if (blit_region_is_unsafe(s, s->cirrus_blt_dstpitch,
-                              s->cirrus_blt_dstaddr & s->cirrus_addr_mask)) {
+                              s->cirrus_blt_dstaddr)) {
         return true;
     }
     if (dst_only) {
         return false;
     }
-    if (blit_region_is_unsafe(s, s->cirrus_blt_srcpitch,
+
-                              s->cirrus_blt_srcaddr & s->cirrus_addr_mask)) {
+    check_pitch = s->cirrus_blt_srcpitch;
+    if (!zero_src_pitch_ok && !check_pitch) {
+        check_pitch = s->cirrus_blt_width;
+    }
+
+    if (blit_region_is_unsafe(s, check_pitch,
+                              s->cirrus_blt_srcaddr)) {
         return true;
     }
 
@@ -661,9 +670,14 @@ static void cirrus_invalidate_region(CirrusVGAState * s, int off_begin,
     int off_cur;
     int off_cur_end;
 
+    if (off_pitch < 0) {
+        off_begin -= bytesperline - 1;
+    }
+
     for (y = 0; y < lines; y++) {
 	off_cur = off_begin;
 	off_cur_end = (off_cur + bytesperline) & s->cirrus_addr_mask;
+        assert(off_cur_end >= off_cur);
         memory_region_set_dirty(&s->vga.vram, off_cur, off_cur_end - off_cur);
 	off_begin += off_pitch;
     }
@@ -674,10 +688,11 @@ static int cirrus_bitblt_common_patterncopy(CirrusVGAState * s,
 {
     uint8_t *dst;
 
-    dst = s->vga.vram_ptr + (s->cirrus_blt_dstaddr & s->cirrus_addr_mask);
+    dst = s->vga.vram_ptr + s->cirrus_blt_dstaddr;
 
-    if (blit_is_unsafe(s, false))
+    if (blit_is_unsafe(s, false, true)) {
         return 0;
+    }
 
     (*s->cirrus_rop) (s, dst, src,
                       s->cirrus_blt_dstpitch, 0,
@@ -694,11 +709,11 @@ static int cirrus_bitblt_solidfill(CirrusVGAState *s, int blt_rop)
 {
     cirrus_fill_t rop_func;
 
-    if (blit_is_unsafe(s, true)) {
+    if (blit_is_unsafe(s, true, true)) {
         return 0;
     }
     rop_func = cirrus_fill[rop_to_index[blt_rop]][s->cirrus_blt_pixelwidth - 1];
-    rop_func(s, s->vga.vram_ptr + (s->cirrus_blt_dstaddr & s->cirrus_addr_mask),
+    rop_func(s, s->vga.vram_ptr + s->cirrus_blt_dstaddr,
              s->cirrus_blt_dstpitch,
              s->cirrus_blt_width, s->cirrus_blt_height);
     cirrus_invalidate_region(s, s->cirrus_blt_dstaddr,
@@ -716,9 +731,8 @@ static int cirrus_bitblt_solidfill(CirrusVGAState *s, int blt_rop)
 
 static int cirrus_bitblt_videotovideo_patterncopy(CirrusVGAState * s)
 {
-    return cirrus_bitblt_common_patterncopy(s,
+    return cirrus_bitblt_common_patterncopy(s, s->vga.vram_ptr +
-					    s->vga.vram_ptr + ((s->cirrus_blt_srcaddr & ~7) &
+                                            (s->cirrus_blt_srcaddr & ~7));
-                                            s->cirrus_addr_mask));
 }
 
 static int cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
@@ -772,10 +786,8 @@ static int cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
     if (notify)
         graphic_hw_update(s->vga.con);
 
-    (*s->cirrus_rop) (s, s->vga.vram_ptr +
+    (*s->cirrus_rop) (s, s->vga.vram_ptr + s->cirrus_blt_dstaddr,
-		      (s->cirrus_blt_dstaddr & s->cirrus_addr_mask),
+                      s->vga.vram_ptr + s->cirrus_blt_srcaddr,
-		      s->vga.vram_ptr +
-		      (s->cirrus_blt_srcaddr & s->cirrus_addr_mask),
 		      s->cirrus_blt_dstpitch, s->cirrus_blt_srcpitch,
 		      s->cirrus_blt_width, s->cirrus_blt_height);
 
@@ -798,7 +810,7 @@ static int cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
 
 static int cirrus_bitblt_videotovideo_copy(CirrusVGAState * s)
 {
-    if (blit_is_unsafe(s, false))
+    if (blit_is_unsafe(s, false, false))
         return 0;
 
     return cirrus_do_copy(s, s->cirrus_blt_dstaddr - s->vga.start_addr,
@@ -826,8 +838,7 @@ static void cirrus_bitblt_cputovideo_next(CirrusVGAState * s)
         } else {
             /* at least one scan line */
             do {
-                (*s->cirrus_rop)(s, s->vga.vram_ptr +
+                (*s->cirrus_rop)(s, s->vga.vram_ptr + s->cirrus_blt_dstaddr,
-                                 (s->cirrus_blt_dstaddr & s->cirrus_addr_mask),
                                   s->cirrus_bltbuf, 0, 0, s->cirrus_blt_width, 1);
                 cirrus_invalidate_region(s, s->cirrus_blt_dstaddr, 0,
                                          s->cirrus_blt_width, 1);
@@ -946,6 +957,9 @@ static void cirrus_bitblt_start(CirrusVGAState * s)
     s->cirrus_blt_modeext = s->vga.gr[0x33];
     blt_rop = s->vga.gr[0x32];
 
+    s->cirrus_blt_dstaddr &= s->cirrus_addr_mask;
+    s->cirrus_blt_srcaddr &= s->cirrus_addr_mask;
+
 #ifdef DEBUG_BITBLT
     printf("rop=0x%02x mode=0x%02x modeext=0x%02x w=%d h=%d dpitch=%d spitch=%d daddr=0x%08x saddr=0x%08x writemask=0x%02x\n",
            blt_rop,