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vnc: deal with surface NULL pointers 

Secondary displays in multihead setups are allowed to have a NULL
DisplaySurface.  Typically user interfaces handle this by hiding the
window which shows the display in question.

This isn't an option for vnc though because it simply hasn't a concept
of windows or outputs.  So handle the situation by showing a placeholder
DisplaySurface instead.  Also check in console_select whenever a surface
is preset in the first place before requesting an update.

This fixes a segfault which can be triggered by switching to an unused
display (via vtrl-alt-<nr>) in a multihead setup, for example using
-device virtio-vga,max_outputs=2.

Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-id: 20180308161803.6152-1-kraxel@redhat.com
This commit is contained in:
Gerd Hoffmann 2018-03-08 17:18:03 +01:00
parent f1bd313264
commit 2e5567c903
3 changed files with 18 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/ui/console.h
View File

@ -260,6 +260,8 @@ DisplaySurface *qemu_create_displaysurface_guestmem(int width, int height,
pixman_format_code_t format,
int linesize,
uint64_t addr);
DisplaySurface *qemu_create_message_surface(int w, int h,
const char *msg);
PixelFormat qemu_default_pixelformat(int bpp);
DisplaySurface *qemu_create_displaysurface(int width, int height);

10
ui/console.c
View File

@ -1039,8 +1039,10 @@ void console_select(unsigned int index)
dcl->ops->dpy_gfx_switch(dcl, s->surface);
}
}
dpy_gfx_update(s, 0, 0, surface_width(s->surface),
surface_height(s->surface));
if (s->surface) {
dpy_gfx_update(s, 0, 0, surface_width(s->surface),
surface_height(s->surface));
}
}
if (ds->have_text) {
dpy_text_resize(s, s->width, s->height);
@ -1370,8 +1372,8 @@ DisplaySurface *qemu_create_displaysurface_guestmem(int width, int height,
return surface;
}
static DisplaySurface *qemu_create_message_surface(int w, int h,
const char *msg)
DisplaySurface *qemu_create_message_surface(int w, int h,
const char *msg)
{
DisplaySurface *surface = qemu_create_displaysurface(w, h);
pixman_color_t bg = color_table_rgb[0][QEMU_COLOR_BLACK];

10
ui/vnc.c
View File

@ -746,9 +746,19 @@ static void vnc_update_server_surface(VncDisplay *vd)
static void vnc_dpy_switch(DisplayChangeListener *dcl,
DisplaySurface *surface)
{
static const char placeholder_msg[] =
"Display output is not active.";
static DisplaySurface *placeholder;
VncDisplay *vd = container_of(dcl, VncDisplay, dcl);
VncState *vs;
if (surface == NULL) {
if (placeholder == NULL) {
placeholder = qemu_create_message_surface(640, 480, placeholder_msg);
}
surface = placeholder;
}
vnc_abort_display_jobs(vd);
vd->ds = surface;