From 84a7b7741a62ede8ff01ae151e59b2a16bda629b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Sat, 23 May 2020 21:15:16 +0200 Subject: hw/display/artist: Refactor artist_rop8() to avoid buffer over-run MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Invalid I/O writes can craft an offset out of the vram_buffer range. Instead of passing an unsafe pointer to artist_rop8(), pass the vram_buffer and the offset. We can now check if the offset is in range before accessing it. We avoid: Program terminated with signal SIGSEGV, Segmentation fault. 284 *dst &= ~plane_mask; (gdb) bt #0 0x000056367b2085c0 in artist_rop8 (s=0x56367d38b510, dst=0x7f9f972fffff , val=0 '\000') at hw/display/artist.c:284 #1 0x000056367b209325 in draw_line (s=0x56367d38b510, x1=-20480, y1=-1, x2=0, y2=17920, update_start=true, skip_pix=-1, max_pix=-1) at hw/display/artist.c:646 Reported-by: LLVM libFuzzer Buglink: https://bugs.launchpad.net/qemu/+bug/1880326 Signed-off-by: Philippe Mathieu-Daudé Signed-off-by: Helge Deller --- hw/display/artist.c | 40 +++++++++++++++++++++++++--------------- 1 file changed, 25 insertions(+), 15 deletions(-) diff --git a/hw/display/artist.c b/hw/display/artist.c index a206afe641..47de17b9e9 100644 --- a/hw/display/artist.c +++ b/hw/display/artist.c @@ -273,11 +273,20 @@ static artist_rop_t artist_get_op(ARTISTState *s) return (s->image_bitmap_op >> 8) & 0xf; } -static void artist_rop8(ARTISTState *s, uint8_t *dst, uint8_t val) +static void artist_rop8(ARTISTState *s, struct vram_buffer *buf, + int offset, uint8_t val) { - const artist_rop_t op = artist_get_op(s); - uint8_t plane_mask = s->plane_mask & 0xff; + uint8_t plane_mask; + uint8_t *dst; + + if (offset < 0 || offset >= buf->size) { + qemu_log_mask(LOG_GUEST_ERROR, + "rop8 offset:%d bufsize:%u\n", offset, buf->size); + return; + } + dst = buf->data + offset; + plane_mask = s->plane_mask & 0xff; switch (op) { case ARTIST_ROP_CLEAR: @@ -375,7 +384,7 @@ static void vram_bit_write(ARTISTState *s, int posx, int posy, bool incr_x, for (i = 0; i < pix_count; i++) { uint32_t off = offset + pix_count - 1 - i; if (off < buf->size) { - artist_rop8(s, p + off, + artist_rop8(s, buf, off, (data & 1) ? (s->plane_mask >> 24) : 0); } data >>= 1; @@ -395,7 +404,7 @@ static void vram_bit_write(ARTISTState *s, int posx, int posy, bool incr_x, s->vram_bitmask & (1 << (28 + i))) { uint32_t off = offset + 3 - i; if (off < buf->size) { - artist_rop8(s, p + off, data8[ROP8OFF(i)]); + artist_rop8(s, buf, off, data8[ROP8OFF(i)]); } } } @@ -424,10 +433,10 @@ static void vram_bit_write(ARTISTState *s, int posx, int posy, bool incr_x, if (!(s->image_bitmap_op & 0x20000000) || (vram_bitmask & mask)) { if (data & mask) { - artist_rop8(s, p + offset + i, s->fg_color); + artist_rop8(s, buf, offset + i, s->fg_color); } else { if (!(s->image_bitmap_op & 0x10000002)) { - artist_rop8(s, p + offset + i, s->bg_color); + artist_rop8(s, buf, offset + i, s->bg_color); } } } @@ -505,7 +514,7 @@ static void block_move(ARTISTState *s, int source_x, int source_y, int dest_x, if (dst + column > buf->size || src + column > buf->size) { continue; } - artist_rop8(s, buf->data + dst + column, buf->data[src + column]); + artist_rop8(s, buf, dst + column, buf->data[src + column]); } } @@ -546,7 +555,7 @@ static void fill_window(ARTISTState *s, int startx, int starty, offset = y * s->width; for (x = startx; x < startx + width; x++) { - artist_rop8(s, buf->data + offset + x, color); + artist_rop8(s, buf, offset + x, color); } } artist_invalidate_lines(buf, starty, height); @@ -559,7 +568,6 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2, uint8_t color; int dx, dy, t, e, x, y, incy, diago, horiz; bool c1; - uint8_t *p; trace_artist_draw_line(x1, y1, x2, y2); @@ -628,16 +636,18 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2, color = artist_get_color(s); do { + int ofs; + if (c1) { - p = buf->data + x * s->width + y; + ofs = x * s->width + y; } else { - p = buf->data + y * s->width + x; + ofs = y * s->width + x; } if (skip_pix > 0) { skip_pix--; } else { - artist_rop8(s, p, color); + artist_rop8(s, buf, ofs, color); } if (e > 0) { @@ -771,10 +781,10 @@ static void font_write16(ARTISTState *s, uint16_t val) for (i = 0; i < 16; i++) { mask = 1 << (15 - i); if (val & mask) { - artist_rop8(s, buf->data + offset + i, color); + artist_rop8(s, buf, offset + i, color); } else { if (!(s->image_bitmap_op & 0x20000000)) { - artist_rop8(s, buf->data + offset + i, s->bg_color); + artist_rop8(s, buf, offset + i, s->bg_color); } } } -- cgit v1.2.3