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[88.21.202.17]) by smtp.gmail.com with ESMTPSA id y185sm13370681wmy.11.2020.05.23.12.15.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 23 May 2020 12:15:22 -0700 (PDT) From: =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= To: Helge Deller , qemu-devel@nongnu.org, Richard Henderson , Sven Schnelle Subject: [PATCH 2/3] hw/display/artist: Refactor artist_rop8() to avoid buffer over-run Date: Sat, 23 May 2020 21:15:16 +0200 Message-Id: <20200523191517.23684-3-f4bug@amsat.org> X-Mailer: git-send-email 2.21.3 In-Reply-To: <20200523191517.23684-1-f4bug@amsat.org> References: <20200523191517.23684-1-f4bug@amsat.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::441; envelope-from=philippe.mathieu.daude@gmail.com; helo=mail-wr1-x441.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.001, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexander Bulekov , =?utf-8?q?Philippe_Mathieu-Daud?= =?utf-8?b?w6k=?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 --- 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 3c2550f6db..6f61b85a24 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: @@ -381,7 +390,7 @@ static void vram_bit_write(ARTISTState *s, int posx, int posy, bool incr_x, } for (i = 0; i < pix_count; i++) { - artist_rop8(s, p + offset + pix_count - 1 - i, + artist_rop8(s, buf, offset + pix_count - 1 - i, (data & 1) ? (s->plane_mask >> 24) : 0); data >>= 1; } @@ -398,7 +407,7 @@ static void vram_bit_write(ARTISTState *s, int posx, int posy, bool incr_x, for (i = 3; i >= 0; i--) { if (!(s->image_bitmap_op & 0x20000000) || s->vram_bitmask & (1 << (28 + i))) { - artist_rop8(s, p + offset + 3 - i, data8[ROP8OFF(i)]); + artist_rop8(s, buf, offset + 3 - i, data8[ROP8OFF(i)]); } } memory_region_set_dirty(&buf->mr, offset, 3); @@ -426,10 +435,10 @@ 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); } } } @@ -507,7 +516,7 @@ 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]); } } @@ -548,7 +557,7 @@ 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); @@ -561,7 +570,6 @@ 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); @@ -630,16 +638,18 @@ 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) { @@ -773,10 +783,10 @@ 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); } } }