From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54014) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPptd-0003jU-28 for qemu-devel@nongnu.org; Fri, 05 Sep 2014 05:33:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XPptX-0007Ux-Bl for qemu-devel@nongnu.org; Fri, 05 Sep 2014 05:33:33 -0400 Message-ID: <1409909600.20018.11.camel@nilsson.home.kraxel.org> From: Gerd Hoffmann Date: Fri, 05 Sep 2014 11:33:20 +0200 In-Reply-To: <54097D07.6020607@redhat.com> References: <1409814273-11463-1-git-send-email-kraxel@redhat.com> <1409814273-11463-4-git-send-email-kraxel@redhat.com> <54096BC2.7070102@redhat.com> <1409907491.20018.5.camel@nilsson.home.kraxel.org> <54097D07.6020607@redhat.com> Content-Type: multipart/mixed; boundary="=-76S7h+BSfoE28HEGKe1E" Mime-Version: 1.0 Subject: Re: [Qemu-devel] [CVE-2014-3615 PATCH v2 3/3] spice: make sure we don't overflow ssd->buf List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: Petr Matousek , secalert@redhat.com, qemu-stable@nongnu.org, qemu-devel@nongnu.org, P J P , Anthony Liguori , spice-devel@lists.freedesktop.org --=-76S7h+BSfoE28HEGKe1E Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit On Fr, 2014-09-05 at 11:06 +0200, Laszlo Ersek wrote: > > Makes sense. I think it is easier to just multiply in 64bit, then > check > > the result is small enougth (new patch attached). > > Okay, if you can guarantee that the product fits in uint64_t, then > such > a check would suffice. > > New patch has not been attached though :) Oops. Here we go. cheers, Gerd --=-76S7h+BSfoE28HEGKe1E Content-Disposition: attachment; filename="0001-spice-make-sure-we-don-t-overflow-ssd-buf.patch" Content-Type: text/x-patch; name="0001-spice-make-sure-we-don-t-overflow-ssd-buf.patch"; charset="UTF-8" Content-Transfer-Encoding: 7bit >>From 33c5c3d1736fd577fc1279a1f3c50d2414e98fe3 Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann Date: Wed, 3 Sep 2014 15:50:08 +0200 Subject: [PATCH] spice: make sure we don't overflow ssd->buf Related spice-only bug. We have a fixed 16 MB buffer here, being presented to the spice-server as qxl video memory in case spice is used with a non-qxl card. It's also used with qxl in vga mode. When using display resolutions requiring more than 16 MB of memory we are going to overflow that buffer. In theory the guest can write, indirectly via spice-server. The spice-server clears the memory after setting a new video mode though, triggering a segfault in the overflow case, so qemu crashes before the guest has a chance to do something evil. Fix that by switching to dynamic allocation for the buffer. CVE-2014-3615 Cc: qemu-stable@nongnu.org Cc: secalert@redhat.com Cc: Laszlo Ersek Signed-off-by: Gerd Hoffmann --- ui/spice-display.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/ui/spice-display.c b/ui/spice-display.c index 66e2578..def7b52 100644 --- a/ui/spice-display.c +++ b/ui/spice-display.c @@ -334,11 +334,23 @@ void qemu_spice_create_host_memslot(SimpleSpiceDisplay *ssd) void qemu_spice_create_host_primary(SimpleSpiceDisplay *ssd) { QXLDevSurfaceCreate surface; + uint64_t surface_size; memset(&surface, 0, sizeof(surface)); - dprint(1, "%s/%d: %dx%d\n", __func__, ssd->qxl.id, - surface_width(ssd->ds), surface_height(ssd->ds)); + surface_size = (uint64_t) surface_width(ssd->ds) * + surface_height(ssd->ds) * 4; + assert(surface_size > 0); + assert(surface_size < INT_MAX); + if (ssd->bufsize < surface_size) { + ssd->bufsize = surface_size; + g_free(ssd->buf); + ssd->buf = g_malloc(ssd->bufsize); + } + + dprint(1, "%s/%d: %ux%u (size %" PRIu64 "/%d)\n", __func__, ssd->qxl.id, + surface_width(ssd->ds), surface_height(ssd->ds), + surface_size, ssd->bufsize); surface.format = SPICE_SURFACE_FMT_32_xRGB; surface.width = surface_width(ssd->ds); @@ -369,8 +381,6 @@ void qemu_spice_display_init_common(SimpleSpiceDisplay *ssd) if (ssd->num_surfaces == 0) { ssd->num_surfaces = 1024; } - ssd->bufsize = (16 * 1024 * 1024); - ssd->buf = g_malloc(ssd->bufsize); } /* display listener callbacks */ @@ -495,7 +505,7 @@ static void interface_get_init_info(QXLInstance *sin, QXLDevInitInfo *info) info->num_memslots = NUM_MEMSLOTS; info->num_memslots_groups = NUM_MEMSLOTS_GROUPS; info->internal_groupslot_id = 0; - info->qxl_ram_size = ssd->bufsize; + info->qxl_ram_size = 16 * 1024 * 1024; info->n_surfaces = ssd->num_surfaces; } -- 1.8.3.1 --=-76S7h+BSfoE28HEGKe1E--