File 0261-vga-check-the-validation-of-memory-.patch of Package qemu-testsuite.20756

Overview Repositories Revisions Requests Users Attributes Meta

File 0261-vga-check-the-validation-of-memory-.patch of Package qemu-testsuite.20756

From: linzhecheng <linzhecheng@huawei.com>
Date: Thu, 11 Jan 2018 21:27:24 +0800
Subject: vga: check the validation of memory addr when draw text

Start a vm with qemu-kvm -enable-kvm -vnc :66 -smp 1 -m 1024 -hda
redhat_5.11.qcow2  -device pcnet -vga cirrus,
then use VNC client to connect to VM, and excute the code below in guest
OS will lead to qemu crash:

int main()
 {
    iopl(3);
    srand(time(NULL));
    int a,b;
    while(1){
	a = rand()%0x100;
	b = 0x3c0 + (rand()%0x20);
        outb(a,b);
    }
    return 0;
}

The above code is writing the registers of VGA randomly.
We can write VGA CRT controller registers index 0x0C or 0x0D
(which is the start address register) to modify the
the display memory address of the upper left pixel
or character of the screen. The address may be out of the
range of vga ram. So we should check the validation of memory address
when reading or writing it to avoid segfault.

Signed-off-by: linzhecheng <linzhecheng@huawei.com>
Message-id: 20180111132724.13744-1-linzhecheng@huawei.com
Fixes: CVE-2018-5683
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 191f59dc17396bb5a8da50f8c59b6e0a430711a4)
[LY: BSC#1076114 CVE-2018-5683]
Signed-off-by: Liang Yan <lyan@suse.com>
---
 hw/display/vga.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/display/vga.c b/hw/display/vga.c
index e737a75db4199388329d7cebe091..fc83e03e4c6567005d352a178390 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1293,6 +1293,9 @@ static void vga_draw_text(VGACommonState *s, int full_update)
         cx_min = width;
         cx_max = -1;
         for(cx = 0; cx < width; cx++) {
+            if (src + sizeof(uint16_t) > s->vram_ptr + s->vram_size) {
+                break;
+            }
             ch_attr = *(uint16_t *)src;
             if (full_update || ch_attr != *ch_attr_ptr || src == cursor_ptr) {
                 if (cx < cx_min)

Places

File 0261-vga-check-the-validation-of-memory-.patch of Package qemu-testsuite.20756

Places