35 lines
1.3 KiB
Diff
35 lines
1.3 KiB
Diff
From f3afa24da144409a3c3a0e35913112583d987671 Mon Sep 17 00:00:00 2001
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From: Michal Srb <michalsrb@gmail.com>
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Date: Mon, 27 Mar 2017 19:02:15 +0300
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Subject: Prevent double free by crafted fences.
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If client sent fence with some data, followed by fence with no data (length 0), the original fence data were freed, but the pointer kept pointing at them. Sending one more fence would attempt to free them again.
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diff --git a/common/rfb/SMsgWriter.cxx b/common/rfb/SMsgWriter.cxx
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index cf3264e..bc3f439 100644
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--- a/common/rfb/SMsgWriter.cxx
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+++ b/common/rfb/SMsgWriter.cxx
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@@ -101,7 +101,9 @@ void SMsgWriter::writeFence(rdr::U32 flags, unsigned len, const char data[])
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os->writeU32(flags);
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os->writeU8(len);
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- os->writeBytes(data, len);
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+
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+ if (len > 0)
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+ os->writeBytes(data, len);
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endMsg();
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}
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diff --git a/common/rfb/VNCSConnectionST.cxx b/common/rfb/VNCSConnectionST.cxx
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index 0a2ca33..d2206f9 100644
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--- a/common/rfb/VNCSConnectionST.cxx
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+++ b/common/rfb/VNCSConnectionST.cxx
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@@ -666,6 +666,7 @@ void VNCSConnectionST::fence(rdr::U32 flags, unsigned len, const char data[])
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fenceFlags = flags & (fenceFlagBlockBefore | fenceFlagBlockAfter | fenceFlagSyncNext);
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fenceDataLen = len;
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delete [] fenceData;
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+ fenceData = NULL;
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if (len > 0) {
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fenceData = new char[len];
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memcpy(fenceData, data, len);
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