From b87a7355de04a2771c11824ea791802c052c979c Mon Sep 17 00:00:00 2001 From: =?utf8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Sat, 23 May 2020 21:15:15 +0200 Subject: [PATCH] hw/display/artist: Check offset in draw_line to avoid buffer over-run MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 , 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 Signed-off-by: Helge Deller --- hw/display/artist.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/hw/display/artist.c b/hw/display/artist.c index de56200dbf..a206afe641 100644 --- a/hw/display/artist.c +++ b/hw/display/artist.c @@ -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) { -- 2.11.0