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vnc: Fix stack corruption and other bitmap related bugs 

Commit bc2429b917 introduced
a severe bug (stack corruption).

bitmap_clear was called with a wrong argument
which caused out-of-bound writes to the local variable width_mask.

This bug was detected with QEMU running on windows.
It also occurs with wine:

*** stack smashing detected ***:  terminated
wine: Unhandled illegal instruction at address 0x6115c7 (thread 0009), starting debugger...

The bug is not windows specific!

Instead of fixing the wrong parameter value, bitmap_clear(), bitmap_set
and width_mask were removed, and bitmap_intersect() was replaced by
!bitmap_empty(). The new operation is much shorter and equivalent to
the old operations.

The declarations of the dirty bitmaps in vnc.h were also wrong for 64 bit
hosts because of a rounding effect: for these hosts, VNC_MAX_WIDTH is no
longer a multiple of (16 * BITS_PER_LONG), so the rounded value of
VNC_DIRTY_WORDS was too small.

Fix both declarations by using the macro which is designed for this
purpose.

Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Gerhard Wiesinger <lists@wiesinger.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Stefan Weil 2011-03-03 21:37:55 +01:00 committed by Anthony Liguori
parent 2ea720dba5
commit 23bfe28fff
2 changed files with 7 additions and 8 deletions
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6
ui/vnc.c
View File

@ -2383,7 +2383,6 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
uint8_t *guest_row;
uint8_t *server_row;
int cmp_bytes;
unsigned long width_mask[VNC_DIRTY_WORDS];
VncState *vs;
int has_dirty = 0;
@ -2399,14 +2398,11 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
* Check and copy modified bits from guest to server surface.
* Update server dirty map.
*/
bitmap_set(width_mask, 0, (ds_get_width(vd->ds) / 16));
bitmap_clear(width_mask, (ds_get_width(vd->ds) / 16),
VNC_DIRTY_WORDS * BITS_PER_LONG);
cmp_bytes = 16 * ds_get_bytes_per_pixel(vd->ds);
guest_row = vd->guest.ds->data;
server_row = vd->server->data;
for (y = 0; y < vd->guest.ds->height; y++) {
if (bitmap_intersects(vd->guest.dirty[y], width_mask, VNC_DIRTY_WORDS)) {
if (!bitmap_empty(vd->guest.dirty[y], VNC_DIRTY_BITS)) {
int x;
uint8_t *guest_ptr;
uint8_t *server_ptr;

9
ui/vnc.h
View File

@ -79,9 +79,12 @@ typedef void VncSendHextileTile(VncState *vs,
void *last_fg,
int *has_bg, int *has_fg);
/* VNC_MAX_WIDTH must be a multiple of 16. */
#define VNC_MAX_WIDTH 2560
#define VNC_MAX_HEIGHT 2048
#define VNC_DIRTY_WORDS (VNC_MAX_WIDTH / (16 * BITS_PER_LONG))
/* VNC_DIRTY_BITS is the number of bits in the dirty bitmap. */
#define VNC_DIRTY_BITS (VNC_MAX_WIDTH / 16)
#define VNC_STAT_RECT 64
#define VNC_STAT_COLS (VNC_MAX_WIDTH / VNC_STAT_RECT)
@ -114,7 +117,7 @@ typedef struct VncRectStat VncRectStat;
struct VncSurface
{
struct timeval last_freq_check;
unsigned long dirty[VNC_MAX_HEIGHT][VNC_DIRTY_WORDS];
DECLARE_BITMAP(dirty[VNC_MAX_HEIGHT], VNC_MAX_WIDTH / 16);
VncRectStat stats[VNC_STAT_ROWS][VNC_STAT_COLS];
DisplaySurface *ds;
};
@ -234,7 +237,7 @@ struct VncState
int csock;
DisplayState *ds;
unsigned long dirty[VNC_MAX_HEIGHT][VNC_DIRTY_WORDS];
DECLARE_BITMAP(dirty[VNC_MAX_HEIGHT], VNC_DIRTY_BITS);
uint8_t **lossy_rect; /* Not an Array to avoid costly memcpy in
* vnc-jobs-async.c */