1 files changed, 54 insertions, 0 deletions
diff --git a/system/xen/xsa/xsa209-qemut.patch b/system/xen/xsa/xsa209-qemut.patch
new file mode 100644
index 0000000000..444beeb2e1
--- /dev/null
+++ b/system/xen/xsa/xsa209-qemut.patch
@@ -0,0 +1,54 @@
+From: Gerd Hoffmann <kraxel@redhat.com>
+Subject: [PATCH 3/3] cirrus: add blit_is_unsafe call to cirrus_bitblt_cputovideo
+
+CIRRUS_BLTMODE_MEMSYSSRC blits do NOT check blit destination
+and blit width, at all.  Oops.  Fix it.
+
+Security impact: high.
+
+The missing blit destination check allows to write to host memory.
+Basically same as CVE-2014-8106 for the other blit variants.
+
+The missing blit width check allows to overflow cirrus_bltbuf,
+with the attractive target cirrus_srcptr (current cirrus_bltbuf write
+position) being located right after cirrus_bltbuf in CirrusVGAState.
+
+Due to cirrus emulation writing cirrus_bltbuf bytewise the attacker
+hasn't full control over cirrus_srcptr though, only one byte can be
+changed.  Once the first byte has been modified further writes land
+elsewhere.
+
+[ This is CVE-2017-2620 / XSA-209  - Ian Jackson ]
+
+Fixed compilation by removing extra parameter to blit_is_unsafe. -iwj
+
+Reported-by: Gerd Hoffmann <ghoffman@redhat.com>
+Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
+Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
+---
+diff --git a/hw/cirrus_vga.c b/hw/cirrus_vga.c
+index e6c3893..45facb6 100644
+--- a/hw/cirrus_vga.c
++++ b/hw/cirrus_vga.c
+@@ -900,6 +900,10 @@ static int cirrus_bitblt_cputovideo(CirrusVGAState * s)
+ {
+     int w;
+ 
++    if (blit_is_unsafe(s)) {
++        return 0;
++    }
++
+     s->cirrus_blt_mode &= ~CIRRUS_BLTMODE_MEMSYSSRC;
+     s->cirrus_srcptr = &s->cirrus_bltbuf[0];
+     s->cirrus_srcptr_end = &s->cirrus_bltbuf[0];
+@@ -925,6 +929,10 @@ static int cirrus_bitblt_cputovideo(CirrusVGAState * s)
+ 	}
+         s->cirrus_srccounter = s->cirrus_blt_srcpitch * s->cirrus_blt_height;
+     }
++
++    /* the blit_is_unsafe call above should catch this */
++    assert(s->cirrus_blt_srcpitch <= CIRRUS_BLTBUFSIZE);
++
+     s->cirrus_srcptr = s->cirrus_bltbuf;
+     s->cirrus_srcptr_end = s->cirrus_bltbuf + s->cirrus_blt_srcpitch;
+     cirrus_update_memory_access(s);