From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=53984 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PvJL9-000680-HR for qemu-devel@nongnu.org; Thu, 03 Mar 2011 19:57:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PvJL8-0003Qi-Dr for qemu-devel@nongnu.org; Thu, 03 Mar 2011 19:57:55 -0500 Received: from na3sys010aog104.obsmtp.com ([74.125.245.76]:43143) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1PvJL8-0003QQ-34 for qemu-devel@nongnu.org; Thu, 03 Mar 2011 19:57:54 -0500 Received: by mail-yw0-f49.google.com with SMTP id 8so623819ywa.36 for ; Thu, 03 Mar 2011 16:57:50 -0800 (PST) Sender: Roland Dreier From: Roland Dreier Date: Thu, 3 Mar 2011 16:57:45 -0800 Message-Id: <1299200265-32685-1-git-send-email-roland@kernel.org> Subject: [Qemu-devel] [PATCH] vnc: tight: Fix crash after 2GB of output List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Roland Dreier , qemu-devel@nongnu.org From: Roland Dreier If one leaves a VNC session with tight compression running for long enough, Qemu crashes. This is because of the computation bytes = zstream->total_out - previous_out; in tight_compress_data, where zstream->total_out is a uLong but previous_out is an int. As soon as zstream->total_out gets past INT_MAX (ie 2GB), previous_out becomes negative and therefore the result of the subtraction, bytes, becomes a huge positive number that causes havoc for obvious reasons when passed as a length to vnc_write(). The fix for this is simple: keep previous_out as a uLong too, which avoids any problems with sign conversion or truncation. Signed-off-by: Roland Dreier --- ui/vnc-enc-tight.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/ui/vnc-enc-tight.c b/ui/vnc-enc-tight.c index af45edd..59ec0e3 100644 --- a/ui/vnc-enc-tight.c +++ b/ui/vnc-enc-tight.c @@ -829,7 +829,7 @@ static int tight_compress_data(VncState *vs, int stream_id, size_t bytes, int level, int strategy) { z_streamp zstream = &vs->tight.stream[stream_id]; - int previous_out; + uLong previous_out; if (bytes < VNC_TIGHT_MIN_TO_COMPRESS) { vnc_write(vs, vs->tight.tight.buffer, vs->tight.tight.offset);