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hw/display/artist: Check offset in draw_line to avoid buffer over-run

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Invalid I/O writes can craft an offset out of the vram_buffer range.

We avoid:

  Program terminated with signal SIGSEGV, Segmentation fault.
  284             *dst &= ~plane_mask;
  (gdb) bt
  #0  0x000055d5dccdc5c0 in artist_rop8 (s=0x55d5defee510, dst=0x7f8e84ed8216 <error: Cannot access memory at address 0x7f8e84ed8216>, val=0 '\000') at hw/display/artist.c:284
  #1  0x000055d5dccdcf83 in fill_window (s=0x55d5defee510, startx=22, starty=5674, width=65, height=5697) at hw/display/artist.c:551
  #2  0x000055d5dccddfb9 in artist_reg_write (opaque=0x55d5defee510, addr=1051140, val=4265537, size=4) at hw/display/artist.c:902
  #3  0x000055d5dcb42a7c in memory_region_write_accessor (mr=0x55d5defeea10, addr=1051140, value=0x7ffe57db08c8, size=4, shift=0, mask=4294967295, attrs=...) at memory.c:483

Reported-by: LLVM libFuzzer
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Philippe Mathieu-Daudé 2020-05-23 21:15:15 +02:00 committed by Helge Deller
parent b899fe41ce
commit b87a7355de
1 changed files with 7 additions and 2 deletions
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9
hw/display/artist.c
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@ -555,7 +555,7 @@ static void fill_window(ARTISTState *s, int startx, int starty,
static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2,
bool update_start, int skip_pix, int max_pix)
{
struct vram_buffer *buf;
struct vram_buffer *buf = &s->vram_buffer[ARTIST_BUFFER_AP];
uint8_t color;
int dx, dy, t, e, x, y, incy, diago, horiz;
bool c1;
@ -563,6 +563,12 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2,
trace_artist_draw_line(x1, y1, x2, y2);
if (x1 * y1 >= buf->size || x2 * y2 >= buf->size) {
qemu_log_mask(LOG_GUEST_ERROR,
"draw_line (%d,%d) (%d,%d)\n", x1, y1, x2, y2);
return;
}
if (update_start) {
s->vram_start = (x2 << 16) | y2;
}
@ -620,7 +626,6 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2,
x = x1;
y = y1;
color = artist_get_color(s);
buf = &s->vram_buffer[ARTIST_BUFFER_AP];
do {
if (c1) {