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Fix stack buffer overflow.
CVE: CVE-2020-35492
Upstream-Status: Backport
Signed-off-by: Ross Burton <ross.burton@arm.com>
From 03a820b173ed1fdef6ff14b4468f5dbc02ff59be Mon Sep 17 00:00:00 2001
From: Heiko Lewin <heiko.lewin@worldiety.de>
Date: Tue, 15 Dec 2020 16:48:19 +0100
Subject: [PATCH] Fix mask usage in image-compositor
---
src/cairo-image-compositor.c | 8 ++--
test/Makefile.sources | 1 +
test/bug-image-compositor.c | 39 ++++++++++++++++++++
test/reference/bug-image-compositor.ref.png | Bin 0 -> 185 bytes
4 files changed, 44 insertions(+), 4 deletions(-)
create mode 100644 test/bug-image-compositor.c
create mode 100644 test/reference/bug-image-compositor.ref.png
diff --git a/src/cairo-image-compositor.c b/src/cairo-image-compositor.c
index 79ad69f68..4f8aaed99 100644
--- a/src/cairo-image-compositor.c
+++ b/src/cairo-image-compositor.c
@@ -2601,14 +2601,14 @@ _inplace_src_spans (void *abstract_renderer, int y, int h,
unsigned num_spans)
{
cairo_image_span_renderer_t *r = abstract_renderer;
- uint8_t *m;
+ uint8_t *m, *base = (uint8_t*)pixman_image_get_data(r->mask);
int x0;
if (num_spans == 0)
return CAIRO_STATUS_SUCCESS;
x0 = spans[0].x;
- m = r->_buf;
+ m = base;
do {
int len = spans[1].x - spans[0].x;
if (len >= r->u.composite.run_length && spans[0].coverage == 0xff) {
@@ -2655,7 +2655,7 @@ _inplace_src_spans (void *abstract_renderer, int y, int h,
spans[0].x, y,
spans[1].x - spans[0].x, h);
- m = r->_buf;
+ m = base;
x0 = spans[1].x;
} else if (spans[0].coverage == 0x0) {
if (spans[0].x != x0) {
@@ -2684,7 +2684,7 @@ _inplace_src_spans (void *abstract_renderer, int y, int h,
#endif
}
- m = r->_buf;
+ m = base;
x0 = spans[1].x;
} else {
*m++ = spans[0].coverage;
--
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