crobinso pushed to qemu (f21). "CVE-2015-5255: heap memory corruption in vnc_refresh_server_surface (bz #1255899)"

From dedc591ecb776fcab13638811e98706b3f562329 Mon Sep 17 00:00:00 2001
From: Cole Robinson 
Date: Mon, 31 Aug 2015 19:43:11 -0400
Subject: CVE-2015-5255: heap memory corruption in vnc_refresh_server_surface
 (bz #1255899)

diff --git a/0101-vnc-fix-memory-corruption-CVE-2015-5225.patch b/0101-vnc-fix-memory-corruption-CVE-2015-5225.patch
new file mode 100644
index 0000000..9755b43
--- /dev/null
+++ b/0101-vnc-fix-memory-corruption-CVE-2015-5225.patch
@@ -0,0 +1,79 @@
+From: Gerd Hoffmann 
+Date: Mon, 17 Aug 2015 19:56:53 +0200
+Subject: [PATCH] vnc: fix memory corruption (CVE-2015-5225)
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+The _cmp_bytes variable added by commit "bea60dd ui/vnc: fix potential
+memory corruption issues" can become negative.  Result is (possibly
+exploitable) memory corruption.  Reason for that is it uses the stride
+instead of bytes per scanline to apply limits.
+
+For the server surface is is actually fine.  vnc creates that itself,
+there is never any padding and thus scanline length always equals stride.
+
+For the guest surface scanline length and stride are typically identical
+too, but it doesn't has to be that way.  So add and use a new variable
+(guest_ll) for the guest scanline length.  Also rename min_stride to
+line_bytes to make more clear what it actually is.  Finally sprinkle
+in an assert() to make sure we never use a negative _cmp_bytes again.
+
+Reported-by: 范祚至(库特) 
+Reviewed-by: P J P 
+Signed-off-by: Gerd Hoffmann 
+(cherry picked from commit eb8934b0418b3b1d125edddc4fc334a54334a49b)
+---
+ ui/vnc.c | 15 ++++++++++-----
+ 1 file changed, 10 insertions(+), 5 deletions(-)
+
+diff --git a/ui/vnc.c b/ui/vnc.c
+index 87e34ae..dec86da 100644
+--- a/ui/vnc.c
++++ b/ui/vnc.c
+@@ -2689,7 +2689,7 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
+                     pixman_image_get_width(vd->server));
+     int height = MIN(pixman_image_get_height(vd->guest.fb),
+                      pixman_image_get_height(vd->server));
+-    int cmp_bytes, server_stride, min_stride, guest_stride, y = 0;
++    int cmp_bytes, server_stride, line_bytes, guest_ll, guest_stride, y = 0;
+     uint8_t *guest_row0 = NULL, *server_row0;
+     VncState *vs;
+     int has_dirty = 0;
+@@ -2708,17 +2708,21 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
+      * Update server dirty map.
+      */
+     server_row0 = (uint8_t *)pixman_image_get_data(vd->server);
+-    server_stride = guest_stride = pixman_image_get_stride(vd->server);
++    server_stride = guest_stride = guest_ll =
++        pixman_image_get_stride(vd->server);
+     cmp_bytes = MIN(VNC_DIRTY_PIXELS_PER_BIT * VNC_SERVER_FB_BYTES,
+                     server_stride);
+     if (vd->guest.format != VNC_SERVER_FB_FORMAT) {
+         int width = pixman_image_get_width(vd->server);
+         tmpbuf = qemu_pixman_linebuf_create(VNC_SERVER_FB_FORMAT, width);
+     } else {
++        int guest_bpp =
++            PIXMAN_FORMAT_BPP(pixman_image_get_format(vd->guest.fb));
+         guest_row0 = (uint8_t *)pixman_image_get_data(vd->guest.fb);
+         guest_stride = pixman_image_get_stride(vd->guest.fb);
++        guest_ll = pixman_image_get_width(vd->guest.fb) * ((guest_bpp + 7) / 8);
+     }
+-    min_stride = MIN(server_stride, guest_stride);
++    line_bytes = MIN(server_stride, guest_ll);
+ 
+     for (;;) {
+         int x;
+@@ -2749,9 +2753,10 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
+             if (!test_and_clear_bit(x, vd->guest.dirty[y])) {
+                 continue;
+             }
+-            if ((x + 1) * cmp_bytes > min_stride) {
+-                _cmp_bytes = min_stride - x * cmp_bytes;
++            if ((x + 1) * cmp_bytes > line_bytes) {
++                _cmp_bytes = line_bytes - x * cmp_bytes;
+             }
++            assert(_cmp_bytes >= 0);
+             if (memcmp(server_ptr, guest_ptr, _cmp_bytes) == 0) {
+                 continue;
+             }
diff --git a/qemu.spec b/qemu.spec
index 5b8ab9c..2315373 100644
--- a/qemu.spec
+++ b/qemu.spec
@@ -152,7 +152,7 @@
 Summary: QEMU is a FAST! processor emulator
 Name: qemu
 Version: 2.1.3
-Release: 9%{?dist}
+Release: 10%{?dist}
 Epoch: 2
 License: GPLv2+ and LGPLv2+ and BSD
 Group: Development/Tools
@@ -257,6 +257,10 @@ Patch0034: 0034-rtl8139-check-IP-Total-Length-field-CVE-2015-5165.patch
 Patch0035: 0035-rtl8139-skip-offload-on-short-TCP-header-CVE-2015-51.patch
 Patch0036: 0036-rtl8139-check-TCP-Data-Offset-field-CVE-2015-5165.patch

+# CVE-2015-5255: heap memory corruption in vnc_refresh_server_surface
+# (bz #1255899)
+Patch0101: 0101-vnc-fix-memory-corruption-CVE-2015-5225.patch
+
 BuildRequires: SDL2-devel
 BuildRequires: zlib-devel
 BuildRequires: which
@@ -847,6 +851,10 @@ CAC emulation development files.
 %patch0035 -p1
 %patch0036 -p1

+# CVE-2015-5255: heap memory corruption in vnc_refresh_server_surface
+# (bz #1255899)
+%patch0101 -p1
+

%build
 %if %{with kvmonly}
@@ -1626,6 +1634,10 @@ getent passwd qemu >/dev/null || \
 %endif

%changelog
+* Mon Aug 31 2015 Cole Robinson  - 2:2.1.3-10
+- CVE-2015-5255: heap memory corruption in vnc_refresh_server_surface (bz
+  #1255899)
+
 * Tue Aug 11 2015 Cole Robinson  - 2:2.1.3-9
 - Fix crash in qemu_spice_create_display (bz #1163047)
 - CVE-2015-3209: pcnet: multi-tmd buffer overflow in the tx path (bz #1230536)