File 0074-vga-check-the-validation-of-memory-.patch of Package qemu

Overview Repositories Revisions Requests Users Attributes Meta

File 0074-vga-check-the-validation-of-memory-.patch of Package qemu (Revision 7dc9cdcfd0de7fc320636d488550b17f)

Currently displaying revision 7dc9cdcfd0de7fc320636d488550b17f , Show latest

From 0b91449df7724669d106f36bcf106db94cdab12d Mon Sep 17 00:00:00 2001
From: linzhecheng <linzhecheng@huawei.com>
Date: Thu, 11 Jan 2018 21:27:24 +0800
Subject: [PATCH] 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 086509db98..08f969d98a 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1280,6 +1280,9 @@ 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 0074-vga-check-the-validation-of-memory-.patch of Package qemu (Revision 7dc9cdcfd0de7fc320636d488550b17f)

Places