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From 6420a8c59712cce74ad689c0d692982665a785b0 Mon Sep 17 00:00:00 2001
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From: Gerd Hoffmann <kraxel@redhat.com>
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Date: Fri, 20 Oct 2017 11:06:19 +0200
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Subject: [PATCH 4/7] cirrus: fix oob access in mode4and5 write functions
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RH-Author: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: <20171020110619.2541-12-kraxel@redhat.com>
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Patchwork-id: 77403
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O-Subject: [RHEL-7.5 qemu-kvm PATCH 11/11] cirrus: fix oob access in mode4and5 write functions
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Bugzilla: 1501295
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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Move dst calculation into the loop, so we apply the mask on each
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interation and will not overflow vga memory.
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Cc: Prasad J Pandit <pjp@fedoraproject.org>
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Reported-by: Niu Guoxiang <niuguoxiang@huawei.com>
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Message-id: 20171011084314.21752-1-kraxel@redhat.com
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(cherry picked from commit eb38e1bc3740725ca29a535351de94107ec58d51)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/display/cirrus_vga.c | 6 ++----
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 1 file changed, 2 insertions(+), 4 deletions(-)
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diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
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index c1324ab..a07fa9c 100644
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--- a/hw/display/cirrus_vga.c
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+++ b/hw/display/cirrus_vga.c
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@@ -2023,15 +2023,14 @@ static void cirrus_mem_writeb_mode4and5_8bpp(CirrusVGAState * s,
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     unsigned val = mem_value;
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     uint8_t *dst;
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-    dst = s->vga.vram_ptr + (offset &= s->cirrus_addr_mask);
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     for (x = 0; x < 8; x++) {
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+        dst = s->vga.vram_ptr + ((offset + x) & s->cirrus_addr_mask);
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 	if (val & 0x80) {
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 	    *dst = s->cirrus_shadow_gr1;
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 	} else if (mode == 5) {
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 	    *dst = s->cirrus_shadow_gr0;
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 	}
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 	val <<= 1;
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-	dst++;
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     }
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     memory_region_set_dirty(&s->vga.vram, offset, 8);
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 }
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@@ -2045,8 +2044,8 @@ static void cirrus_mem_writeb_mode4and5_16bpp(CirrusVGAState * s,
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     unsigned val = mem_value;
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     uint8_t *dst;
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-    dst = s->vga.vram_ptr + (offset &= s->cirrus_addr_mask);
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     for (x = 0; x < 8; x++) {
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+        dst = s->vga.vram_ptr + ((offset + 2 * x) & s->cirrus_addr_mask & ~1);
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 	if (val & 0x80) {
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 	    *dst = s->cirrus_shadow_gr1;
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 	    *(dst + 1) = s->vga.gr[0x11];
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@@ -2055,7 +2054,6 @@ static void cirrus_mem_writeb_mode4and5_16bpp(CirrusVGAState * s,
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 	    *(dst + 1) = s->vga.gr[0x10];
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 	}
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 	val <<= 1;
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-	dst += 2;
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     }
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     memory_region_set_dirty(&s->vga.vram, offset, 16);
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 }
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-- 
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1.8.3.1
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