qemu: CVE-2017-2620

QEMU built with the Cirrus CLGD 54xx VGA Emulator support
is vulnerable to an out-of-bounds access issue. The issue
could occur while copying VGA data in cirrus_bitblt_cputovideo.

References:
==========
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-2620
Upstream patch:
https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg04700.html

Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
Signed-off-by: Adrian Dudau <adrian.dudau@enea.com>

3 files changed, 138 insertions, 0 deletions

diff --git a/recipes-devtools/qemu/qemu/0001-CVE-2017-2620.patch b/recipes-devtools/qemu/qemu/0001-CVE-2017-2620.patch
new file mode 100644
index 0000000..5684062
--- /dev/null
+++ b/recipes-devtools/qemu/qemu/0001-CVE-2017-2620.patch
@@ -0,0 +1,77 @@
+From 2ab8276a1cb2bcd0d14d4e05c193252f370b8251 Mon Sep 17 00:00:00 2001
+From: Bruce Rogers <brogers@suse.com>
+Date: Mon, 9 Jan 2017 13:35:20 -0700
+Subject: [PATCH] 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.
+
+Upstream-Status: Backport [this patch is needed for CVE-2017-2620]
+
+Signed-off-by: Bruce Rogers <brogers@suse.com>
+Message-id: 20170109203520.5619-1-brogers@suse.com
+Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
+(cherry picked from commit 913a87885f589d263e682c2eb6637c6e14538061)
+Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
+Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
+---
+ hw/display/cirrus_vga.c | 11 +++++++----
+ 1 file changed, 7 insertions(+), 4 deletions(-)
+
+diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
+index bdb092e..379910d 100644
+--- a/hw/display/cirrus_vga.c
++++ b/hw/display/cirrus_vga.c
+@@ -294,7 +294,7 @@ 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);
+@@ -308,6 +308,9 @@ 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;
+@@ -673,7 +676,7 @@ 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,
+@@ -691,7 +694,7 @@ 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];
+@@ -795,7 +798,7 @@ 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))
++    if (blit_is_unsafe(s, false))
+         return 0;
+ 
+     return cirrus_do_copy(s, s->cirrus_blt_dstaddr - s->vga.start_addr,
+-- 
+1.9.1
+
diff --git a/recipes-devtools/qemu/qemu/0002-CVE-2017-2620.patch b/recipes-devtools/qemu/qemu/0002-CVE-2017-2620.patch
new file mode 100644
index 0000000..3910fb9
--- /dev/null
+++ b/recipes-devtools/qemu/qemu/0002-CVE-2017-2620.patch
@@ -0,0 +1,55 @@
+From fc8e94c3e5e74437c4e73a5582f17cfd4cae5ccf Mon Sep 17 00:00:00 2001
+From: Gerd Hoffmann <kraxel@redhat.com>
+Date: Wed, 8 Feb 2017 11:18:36 +0100
+Subject: [PATCH] cirrus: add blit_is_unsafe call to cirrus_bitblt_cputovideo
+ (CVE-2017-2620)
+
+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.
+
+CVE: CVE-2017-2620
+Upstream-Status: Backport
+
+Cc: qemu-stable@nongnu.org
+Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
+(cherry picked from commit 92f2b88cea48c6aeba8de568a45f2ed958f3c298)
+Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
+Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
+---
+ hw/display/cirrus_vga.c | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
+index 629a5c8..6766349 100644
+--- a/hw/display/cirrus_vga.c
++++ b/hw/display/cirrus_vga.c
+@@ -873,6 +873,10 @@ static int cirrus_bitblt_cputovideo(CirrusVGAState * s)
+ {
+     int w;
+ 
++    if (blit_is_unsafe(s, true)) {
++        return 0;
++    }
++
+     s->cirrus_blt_mode &= ~CIRRUS_BLTMODE_MEMSYSSRC;
+     s->cirrus_srcptr = &s->cirrus_bltbuf[0];
+     s->cirrus_srcptr_end = &s->cirrus_bltbuf[0];
+@@ -898,6 +902,10 @@ 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);
+-- 
+1.9.1
+
diff --git a/recipes-devtools/qemu/qemu_%.bbappend b/recipes-devtools/qemu/qemu_%.bbappend
new file mode 100644
index 0000000..96a45b8
--- /dev/null
+++ b/recipes-devtools/qemu/qemu_%.bbappend
@@ -0,0 +1,6 @@
+# look for files in the layer first
+FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+
+SRC_URI += "file://0001-CVE-2017-2620.patch \
+            file://0002-CVE-2017-2620.patch \
+           "