From: Gerd Hoffmann 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. Cc: qemu-stable@nongnu.org Signed-off-by: Gerd Hoffmann (cherry picked from commit 92f2b88cea48c6aeba8de568a45f2ed958f3c298) --- 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 0e47cf85ad..a093dc8b16 100644 --- a/hw/display/cirrus_vga.c +++ b/hw/display/cirrus_vga.c @@ -899,6 +899,10 @@ 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]; @@ -924,6 +928,10 @@ 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);