display: cirrus: ignore source pitch value as needed in blit_is_unsafe

Commit 4299b90 added a check which is too broad, given that the source
pitch value is not required to be initialized for solid fill operations.
This patch refines the blit_is_unsafe() check to ignore source pitch in
that case. After applying the above commit as a security patch, we
noticed the SLES 11 SP4 guest gui failed to initialize properly.

Signed-off-by: Bruce Rogers <brogers@suse.com>
Message-id: 20170109203520.5619-1-brogers@suse.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
index 1a66fcf91d087c3b9517424433e03139ef6e857b..bbe1f433f36f40973abe4600e8b979292cc543a7 100644 (file)
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -286,7 +286,7 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s,
     return false;
 }
 
-static bool blit_is_unsafe(struct CirrusVGAState *s)
+static bool blit_is_unsafe(struct CirrusVGAState *s, bool dst_only)
 {
     /* should be the case, see cirrus_bitblt_start */
     assert(s->cirrus_blt_width > 0);
@@ -300,6 +300,9 @@ static bool blit_is_unsafe(struct CirrusVGAState *s)
                               s->cirrus_blt_dstaddr & s->cirrus_addr_mask)) {
         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)) {
         return true;
@@ -665,7 +668,7 @@ static int cirrus_bitblt_common_patterncopy(CirrusVGAState * s,
 
     dst = s->vga.vram_ptr + (s->cirrus_blt_dstaddr & s->cirrus_addr_mask);
 
-    if (blit_is_unsafe(s))
+    if (blit_is_unsafe(s, false))
         return 0;
 
     (*s->cirrus_rop) (s, dst, src,
@@ -683,7 +686,7 @@ static int cirrus_bitblt_solidfill(CirrusVGAState *s, int blt_rop)
 {
     cirrus_fill_t rop_func;
 
-    if (blit_is_unsafe(s)) {
+    if (blit_is_unsafe(s, true)) {
         return 0;
     }
     rop_func = cirrus_fill[rop_to_index[blt_rop]][s->cirrus_blt_pixelwidth - 1];
@@ -782,7 +785,7 @@ static void cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
 
 static int cirrus_bitblt_videotovideo_copy(CirrusVGAState * s)
 {
-    if (blit_is_unsafe(s))
+    if (blit_is_unsafe(s, false))
         return 0;
 
     cirrus_do_copy(s, s->cirrus_blt_dstaddr - s->vga.start_addr,