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From: "Daniel P. Berrange" <berrange@redhat.com>
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Date: Mon, 9 Oct 2017 14:43:42 +0100
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Subject: [PATCH] io: monitor encoutput buffer size from websocket GSource
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The websocket GSource is monitoring the size of the rawoutput
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buffer to determine if the channel can accepts more writes.
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The rawoutput buffer, however, is merely a temporary staging
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buffer before data is copied into the encoutput buffer. Thus
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its size will always be zero when the GSource runs.
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This flaw causes the encoutput buffer to grow without bound
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if the other end of the underlying data channel doesn't
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read data being sent. This can be seen with VNC if a client
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is on a slow WAN link and the guest OS is sending many screen
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updates. A malicious VNC client can act like it is on a slow
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link by playing a video in the guest and then reading data
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very slowly, causing QEMU host memory to expand arbitrarily.
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This issue is assigned CVE-2017-15268, publically reported in
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https://bugs.launchpad.net/qemu/+bug/1718964
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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(cherry picked from commit a7b20a8efa28e5f22c26c06cd06c2f12bc863493)
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---
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io/channel-websock.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/io/channel-websock.c b/io/channel-websock.c
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index 5a3badbec2..c02c2a66c9 100644
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--- a/io/channel-websock.c
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+++ b/io/channel-websock.c
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@@ -26,7 +26,7 @@
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#include "trace.h"
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-/* Max amount to allow in rawinput/rawoutput buffers */
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+/* Max amount to allow in rawinput/encoutput buffers */
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#define QIO_CHANNEL_WEBSOCK_MAX_BUFFER 8192
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#define QIO_CHANNEL_WEBSOCK_CLIENT_KEY_LEN 24
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@@ -1006,7 +1006,7 @@ qio_channel_websock_source_prepare(GSource *source,
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if (wsource->wioc->rawinput.offset) {
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cond |= G_IO_IN;
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}
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- if (wsource->wioc->rawoutput.offset < QIO_CHANNEL_WEBSOCK_MAX_BUFFER) {
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+ if (wsource->wioc->encoutput.offset < QIO_CHANNEL_WEBSOCK_MAX_BUFFER) {
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cond |= G_IO_OUT;
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}
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