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From: Gerd Hoffmann <kraxel@redhat.com>
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Date: Mon, 30 May 2016 09:09:18 +0200
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Subject: [PATCH] vmsvga: move fifo sanity checks to vmsvga_fifo_length
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Sanity checks are applied when the fifo is enabled by the guest
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(SVGA_REG_CONFIG_DONE write). Which doesn't help much if the guest
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changes the fifo registers afterwards. Move the checks to
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vmsvga_fifo_length so they are done each time qemu is about to read
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from the fifo.
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Fixes: CVE-2016-4454
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Cc: qemu-stable@nongnu.org
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Cc: P J P <ppandit@redhat.com>
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Reported-by: 李强 <liqiang6-s@360.cn>
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: 1464592161-18348-2-git-send-email-kraxel@redhat.com
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(cherry picked from commit 521360267876d3b6518b328051a2e56bca55bef8)
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---
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hw/display/vmware_vga.c | 28 +++++++++++++++-------------
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1 file changed, 15 insertions(+), 13 deletions(-)
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diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c
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index c17ddd1..b12128a 100644
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--- a/hw/display/vmware_vga.c
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+++ b/hw/display/vmware_vga.c
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@@ -553,6 +553,21 @@ static inline int vmsvga_fifo_length(struct vmsvga_state_s *s)
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if (!s->config || !s->enable) {
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return 0;
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}
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+
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+ /* Check range and alignment. */
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+ if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) {
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+ return 0;
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+ }
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+ if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) {
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+ return 0;
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+ }
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+ if (CMD(max) > SVGA_FIFO_SIZE) {
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+ return 0;
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+ }
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+ if (CMD(max) < CMD(min) + 10 * 1024) {
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+ return 0;
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+ }
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+
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num = CMD(next_cmd) - CMD(stop);
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if (num < 0) {
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num += CMD(max) - CMD(min);
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@@ -1000,19 +1015,6 @@ static void vmsvga_value_write(void *opaque, uint32_t address, uint32_t value)
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case SVGA_REG_CONFIG_DONE:
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if (value) {
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s->fifo = (uint32_t *) s->fifo_ptr;
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- /* Check range and alignment. */
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- if ((CMD(min) | CMD(max) | CMD(next_cmd) | CMD(stop)) & 3) {
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- break;
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- }
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- if (CMD(min) < (uint8_t *) s->cmd->fifo - (uint8_t *) s->fifo) {
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- break;
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- }
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- if (CMD(max) > SVGA_FIFO_SIZE) {
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- break;
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- }
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- if (CMD(max) < CMD(min) + 10 * 1024) {
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- break;
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- }
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vga_dirty_log_stop(&s->vga);
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}
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s->config = !!value;
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