[Xen-changelog] [qemu-xen stable-4.6] cirrus: fix oob access issue (CVE-2017-2615)

[patchbot@xxxxxxx]

commit 15c0f1500fc078b6411d2c86842cb2f3fd7393c0
Author:     Li Qiang <liqiang6-s@xxxxxx>
AuthorDate: Thu Feb 9 14:36:41 2017 -0800
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Thu Feb 9 14:44:23 2017 -0800

    cirrus: fix oob access issue (CVE-2017-2615)
    
    When doing bitblt copy in backward mode, we should minus the
    blt width first just like the adding in the forward mode. This
    can avoid the oob access of the front of vga's vram.
    
    This is XSA-208.
    
    upstream-commit-id: 62d4c6bd5263bb8413a06c80144fc678df6dfb64
    
    Signed-off-by: Li Qiang <liqiang6-s@xxxxxx>
    
    { kraxel: with backward blits (negative pitch) addr is the topmost
              address, so check it as-is against vram size ]
    
    Cc: qemu-stable@xxxxxxxxxx
    Cc: P J P <ppandit@xxxxxxxxxx>
    Cc: Laszlo Ersek <lersek@xxxxxxxxxx>
    Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Cc: Wolfgang Bumiller <w.bumiller@xxxxxxxxxxx>
    Fixes: d3532a0db02296e687711b8cdc7791924efccea0 (CVE-2014-8106)
    Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
    Message-id: 1485938101-26602-1-git-send-email-kraxel@xxxxxxxxxx
    Reviewed-by: Laszlo Ersek <lersek@xxxxxxxxxx>
    Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 hw/display/cirrus_vga.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
index 2725264..8f86142 100644
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -270,10 +270,9 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s,
 {
     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->vga.vram_size) {
+            + ((int64_t)s->cirrus_blt_height - 1) * pitch
+            - s->cirrus_blt_width;
+        if (min < -1 || addr >= s->vga.vram_size) {
             return true;
         }
     } else {
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#stable-4.6

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