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From 5d201df72f3d4f4cb8b8f75f980169b03507da38 Mon Sep 17 00:00:00 2001
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From: Tobias Stoeckmann <tobias@stoeckmann.org>
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Date: Tue, 28 Nov 2017 21:38:07 +0100
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Subject: [PATCH] cursor: Fix heap overflows when parsing malicious files.
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It is possible to trigger heap overflows due to an integer overflow
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while parsing images.
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The integer overflow occurs because the chosen limit 0x10000 for
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dimensions is too large for 32 bit systems, because each pixel takes
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4 bytes. Properly chosen values allow an overflow which in turn will
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lead to less allocated memory than needed for subsequent reads.
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See also: https://cgit.freedesktop.org/xorg/lib/libXcursor/commit/?id=4794b5dd34688158fb51a2943032569d3780c4b8
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Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=103961
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Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
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[Pekka: add link to the corresponding libXcursor commit]
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Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
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---
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cursor/xcursor.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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diff --git a/cursor/xcursor.c b/cursor/xcursor.c
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index ca41c4ac611f..689c7026729d 100644
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--- a/cursor/xcursor.c
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+++ b/cursor/xcursor.c
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@@ -202,6 +202,11 @@ XcursorImageCreate (int width, int height)
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{
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XcursorImage *image;
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+ if (width < 0 || height < 0)
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+ return NULL;
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+ if (width > XCURSOR_IMAGE_MAX_SIZE || height > XCURSOR_IMAGE_MAX_SIZE)
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+ return NULL;
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+
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image = malloc (sizeof (XcursorImage) +
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width * height * sizeof (XcursorPixel));
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if (!image)
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@@ -482,7 +487,8 @@ _XcursorReadImage (XcursorFile *file,
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if (!_XcursorReadUInt (file, &head.delay))
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return NULL;
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/* sanity check data */
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- if (head.width >= 0x10000 || head.height > 0x10000)
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+ if (head.width > XCURSOR_IMAGE_MAX_SIZE ||
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+ head.height > XCURSOR_IMAGE_MAX_SIZE)
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return NULL;
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if (head.width == 0 || head.height == 0)
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return NULL;
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--
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2.14.3
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