File kvm-qemu-preXX-vnc-tight-Fix-crash-after-2GB-of... of Package kvm.853

Overview Repositories Revisions Requests Users Attributes Meta

File kvm-qemu-preXX-vnc-tight-Fix-crash-after-2GB-of-output.patch of Package kvm.853

From 2caa9e9d2e0f356cc244bc41ce1d3e81663f6782 Mon Sep 17 00:00:00 2001
From: Michael Tokarev <mjt@tls.msk.ru>
Date: Mon, 21 Mar 2011 09:34:35 +0100
Subject: [PATCH] vnc: tight: Fix crash after 2GB of output

fix 2Gb integer overflow in in VNC tight and zlib encodings

As found by Roland Dreier <roland@purestorage.com> (excellent
catch!), when amount of VNC compressed data produced by zlib
and sent to client exceeds 2Gb, integer overflow occurs because
currently, we calculate amount of data produced at each step by
comparing saved total_out with new total_out, and total_out is
something which grows without bounds.  Compare it with previous
avail_out instead of total_out, and leave total_out alone.

The same code is used in vnc-enc-tight.c and vnc-enc-zlib.c,
so fix both cases.

There, there's no actual need to save previous_out value, since
capacity-offset (which is how that value is calculated) stays
the same so it can be recalculated again after call to deflate(),
but whole thing becomes less readable this way.

Reported-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Corentin Chary <corentin.chary@gmail.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
---
 ui/vnc-enc-tight.c |    5 +++--
 ui/vnc-enc-zlib.c  |    4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/ui/vnc-enc-tight.c b/ui/vnc-enc-tight.c
index 2522936..87fdf35 100644
--- a/ui/vnc-enc-tight.c
+++ b/ui/vnc-enc-tight.c
@@ -868,8 +868,8 @@ static int tight_compress_data(VncState *vs, int stream_id, size_t bytes,
     zstream->avail_in = vs->tight.tight.offset;
     zstream->next_out = vs->tight.zlib.buffer + vs->tight.zlib.offset;
     zstream->avail_out = vs->tight.zlib.capacity - vs->tight.zlib.offset;
+    previous_out = zstream->avail_out;
     zstream->data_type = Z_BINARY;
-    previous_out = zstream->total_out;
 
     /* start encoding */
     if (deflate(zstream, Z_SYNC_FLUSH) != Z_OK) {
@@ -878,7 +878,8 @@ static int tight_compress_data(VncState *vs, int stream_id, size_t bytes,
     }
 
     vs->tight.zlib.offset = vs->tight.zlib.capacity - zstream->avail_out;
-    bytes = zstream->total_out - previous_out;
+    /* ...how much data has actually been produced by deflate() */
+    bytes = previous_out - zstream->avail_out;
 
     tight_send_compact_size(vs, bytes);
     vnc_write(vs, vs->tight.zlib.buffer, bytes);
diff --git a/ui/vnc-enc-zlib.c b/ui/vnc-enc-zlib.c
index 3c6e6ab..e32e4cd 100644
--- a/ui/vnc-enc-zlib.c
+++ b/ui/vnc-enc-zlib.c
@@ -103,8 +103,8 @@ static int vnc_zlib_stop(VncState *vs)
     zstream->avail_in = vs->zlib.zlib.offset;
     zstream->next_out = vs->output.buffer + vs->output.offset;
     zstream->avail_out = vs->output.capacity - vs->output.offset;
+    previous_out = zstream->avail_out;
     zstream->data_type = Z_BINARY;
-    previous_out = zstream->total_out;
 
     // start encoding
     if (deflate(zstream, Z_SYNC_FLUSH) != Z_OK) {
@@ -113,7 +113,7 @@ static int vnc_zlib_stop(VncState *vs)
     }
 
     vs->output.offset = vs->output.capacity - zstream->avail_out;
-    return zstream->total_out - previous_out;
+    return previous_out - zstream->avail_out;
 }
 
 int vnc_zlib_send_framebuffer_update(VncState *vs, int x, int y, int w, int h)
-- 
1.6.0.2

Places

File kvm-qemu-preXX-vnc-tight-Fix-crash-after-2GB-of-output.patch of Package kvm.853

Places