From: Gerd Hoffmann Date: Mon, 30 May 2016 09:09:18 +0200 Subject: [PATCH] vmsvga: move fifo sanity checks to vmsvga_fifo_length MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sanity checks are applied when the fifo is enabled by the guest (SVGA_REG_CONFIG_DONE write). Which doesn't help much if the guest changes the fifo registers afterwards. Move the checks to vmsvga_fifo_length so they are done each time qemu is about to read from the fifo. Fixes: CVE-2016-4454 Cc: qemu-stable@nongnu.org Cc: P J P Reported-by: 李强 Signed-off-by: Gerd Hoffmann Message-id: 1464592161-18348-2-git-send-email-kraxel@redhat.com (cherry picked from commit 521360267876d3b6518b328051a2e56bca55bef8) --- hw/display/vmware_vga.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c index 0c63fa8..63a7c05 100644 --- a/hw/display/vmware_vga.c +++ b/hw/display/vmware_vga.c @@ -555,6 +555,21 @@ static inline int vmsvga_fifo_length(struct vmsvga_state_s *s) if (!s->config || !s->enable) { return 0; } + + /* Check range and alignment. */ + if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) { + return 0; + } + if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) { + return 0; + } + if (CMD(max) > SVGA_FIFO_SIZE) { + return 0; + } + if (CMD(max) < CMD(min) + 10 * 1024) { + return 0; + } + num = CMD(next_cmd) - CMD(stop); if (num < 0) { num += CMD(max) - CMD(min); @@ -1005,19 +1020,6 @@ static void vmsvga_value_write(void *opaque, uint32_t address, uint32_t value) case SVGA_REG_CONFIG_DONE: if (value) { s->fifo = (uint32_t *) s->fifo_ptr; - /* Check range and alignment. */ - if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) { - break; - } - if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) { - break; - } - if (CMD(max) > SVGA_FIFO_SIZE) { - break; - } - if (CMD(max) < CMD(min) + 10 * 1024) { - break; - } vga_dirty_log_stop(&s->vga); } s->config = !!value;