If you find that patch too strict, I have another patch ready (needs some final testing) which works around all the possible corruption issues iff
a) width % VNC_DIRTY_PIXELS_PER_BIT != 0 (while still keep it working) b) width > VNC_MAX_WIDTH || heigth > VNC_MAX_HEIGTH Peter Am 27.06.2014 12:41, schrieb Peter Lieven: > during resolution change in Windows 7 it happens sometimes that Windows > changes to > an intermediate resolution where server_stride % cmp_bytes != 0 (in > vnc_refresh_server_surface). > The problem that causes memory corruption is where the guest fb is copied to > the server fb. > It could be easily fixed by truncating cmp_bytes in > vnc_refresh_server_surface. But by looking at > the code it seems that none of the encoders called in > vnc_send_framebuffer_update really cares about > w > pixman_image_get_width(vd->server). This patch will therefore remove all > DIV_ROUND_UPs for > now to avoid corruption or illegal reads. I think there are really almost no > real resultions out > there where width % 16 != 0. If we really find some we might need to either > decrease > VNC_DIRTY_PIXELS_PER_BIT or make it dynamic depending on the resolution. > > Cc: qemu-sta...@nongnu.org > Signed-off-by: Peter Lieven <p...@kamp.de> > --- > ui/vnc.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/ui/vnc.c b/ui/vnc.c > index 14a86c3..9e37d47 100644 > --- a/ui/vnc.c > +++ b/ui/vnc.c > @@ -577,7 +577,7 @@ void *vnc_server_fb_ptr(VncDisplay *vd, int x, int y) > memset(bitmap, 0x00, sizeof(bitmap));\ > for (y = 0; y < h; y++) {\ > bitmap_set(bitmap[y], 0,\ > - DIV_ROUND_UP(w, VNC_DIRTY_PIXELS_PER_BIT));\ > + w / VNC_DIRTY_PIXELS_PER_BIT);\ > } \ > } > > @@ -2738,7 +2738,7 @@ static int vnc_refresh_server_surface(VncDisplay *vd) > } > guest_ptr += x * cmp_bytes; > > - for (; x < DIV_ROUND_UP(width, VNC_DIRTY_PIXELS_PER_BIT); > + for (; x < width / VNC_DIRTY_PIXELS_PER_BIT; > x++, guest_ptr += cmp_bytes, server_ptr += cmp_bytes) { > if (!test_and_clear_bit(x, vd->guest.dirty[y])) { > continue;