From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1chGAx-0005cl-G7 for qemu-devel@nongnu.org; Fri, 24 Feb 2017 08:44:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1chGAv-0001fK-PF for qemu-devel@nongnu.org; Fri, 24 Feb 2017 08:44:47 -0500 From: Gerd Hoffmann Date: Fri, 24 Feb 2017 14:44:37 +0100 Message-Id: <1487943877-17318-2-git-send-email-kraxel@redhat.com> In-Reply-To: <1487943877-17318-1-git-send-email-kraxel@redhat.com> References: <1487943877-17318-1-git-send-email-kraxel@redhat.com> Subject: [Qemu-devel] [PULL 1/1] cirrus: add blit_is_unsafe call to cirrus_bitblt_cputovideo (CVE-2017-2620) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Gerd Hoffmann , qemu-stable@nongnu.org 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. Cc: qemu-stable@nongnu.org Signed-off-by: Gerd Hoffmann --- 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 1deb520..b9e7cb1 100644 --- a/hw/display/cirrus_vga.c +++ b/hw/display/cirrus_vga.c @@ -900,6 +900,10 @@ 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]; @@ -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); -- 1.8.3.1