[PATCH] ati: mask x y display parameter values

[P J P]

From: Prasad J Pandit <pjp@fedoraproject.org>

The source and destination x,y display parameters in ati_2d_blt()
may run off the vga limits if either of s->regs.[src|dst]_[xy] is
zero. Mask the register values to avoid potential crash.

Reported-by: Gaoning Pan <pgn@zju.edu.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/display/ati_2d.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/hw/display/ati_2d.c b/hw/display/ati_2d.c
index 23a8ae0cd8..524bc03a83 100644
--- a/hw/display/ati_2d.c
+++ b/hw/display/ati_2d.c
@@ -53,10 +53,10 @@ void ati_2d_blt(ATIVGAState *s)
             s->vga.vbe_start_addr, surface_data(ds), surface_stride(ds),
             surface_bits_per_pixel(ds),
             (s->regs.dp_mix & GMC_ROP3_MASK) >> 16);
-    unsigned dst_x = (s->regs.dp_cntl & DST_X_LEFT_TO_RIGHT ?
-                      s->regs.dst_x : s->regs.dst_x + 1 - s->regs.dst_width);
-    unsigned dst_y = (s->regs.dp_cntl & DST_Y_TOP_TO_BOTTOM ?
-                      s->regs.dst_y : s->regs.dst_y + 1 - s->regs.dst_height);
+    unsigned dst_x = (s->regs.dp_cntl & DST_X_LEFT_TO_RIGHT ? s->regs.dst_x
+                        : (s->regs.dst_x + 1 - s->regs.dst_width) & 0x3fff);
+    unsigned dst_y = (s->regs.dp_cntl & DST_Y_TOP_TO_BOTTOM ? s->regs.dst_y
+                        : (s->regs.dst_y + 1 - s->regs.dst_height) & 0x3fff);
     int bpp = ati_bpp_from_datatype(s);
     if (!bpp) {
         qemu_log_mask(LOG_GUEST_ERROR, "Invalid bpp\n");
@@ -91,9 +91,9 @@ void ati_2d_blt(ATIVGAState *s)
     case ROP3_SRCCOPY:
     {
         unsigned src_x = (s->regs.dp_cntl & DST_X_LEFT_TO_RIGHT ?
-                       s->regs.src_x : s->regs.src_x + 1 - s->regs.dst_width);
+           s->regs.src_x : (s->regs.src_x + 1 - s->regs.dst_width) & 0x3fff);
         unsigned src_y = (s->regs.dp_cntl & DST_Y_TOP_TO_BOTTOM ?
-                       s->regs.src_y : s->regs.src_y + 1 - s->regs.dst_height);
+           s->regs.src_y : (s->regs.src_y + 1 - s->regs.dst_height) & 0x3fff);
         int src_stride = DEFAULT_CNTL ?
                          s->regs.src_pitch : s->regs.default_pitch;
         if (!src_stride) {
-- 
2.26.2