Commit 92f2b88c authored by Gerd Hoffmann's avatar Gerd Hoffmann
Browse files

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: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 10f25e48

hw/display/cirrus_vga.c

+8 −0
Original line number Diff line number Diff line
@@ -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);