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From a343de8e9b85b98f18446d045afbf6f1d3f6c5b4 Mon Sep 17 00:00:00 2001
From: "Richard J. Moore" <rich@kde.org>
Date: Sat, 21 Feb 2015 17:43:21 +0000
Subject: [PATCH 14/14] Fix a division by zero when processing malformed BMP
files.
This fixes a division by 0 when processing a maliciously crafted BMP
file. No impact beyond DoS.
Upstream-Status: Backport from 5.4 branch
Task-number: QTBUG-44547
Change-Id: Ifcded2c0aa712e90d23e6b3969af0ec3add53973
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
---
src/gui/image/qbmphandler.cpp | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/src/gui/image/qbmphandler.cpp b/src/gui/image/qbmphandler.cpp
index 21c1a2f..df66499 100644
--- a/src/gui/image/qbmphandler.cpp
+++ b/src/gui/image/qbmphandler.cpp
@@ -314,12 +314,20 @@ static bool read_dib_body(QDataStream &s, const BMP_INFOHDR &bi, int offset, int
}
} else if (comp == BMP_BITFIELDS && (nbits == 16 || nbits == 32)) {
red_shift = calc_shift(red_mask);
+ if (((red_mask >> red_shift) + 1) == 0)
+ return false;
red_scale = 256 / ((red_mask >> red_shift) + 1);
green_shift = calc_shift(green_mask);
+ if (((green_mask >> green_shift) + 1) == 0)
+ return false;
green_scale = 256 / ((green_mask >> green_shift) + 1);
blue_shift = calc_shift(blue_mask);
+ if (((blue_mask >> blue_shift) + 1) == 0)
+ return false;
blue_scale = 256 / ((blue_mask >> blue_shift) + 1);
alpha_shift = calc_shift(alpha_mask);
+ if (((alpha_mask >> alpha_shift) + 1) == 0)
+ return false;
alpha_scale = 256 / ((alpha_mask >> alpha_shift) + 1);
} else if (comp == BMP_RGB && (nbits == 24 || nbits == 32)) {
blue_mask = 0x000000ff;
--
2.3.1
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