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Re: [Qemu-devel] [PATCH v1 00/13] Fix VNC server unbounded memory usage

From: Marc-André Lureau
Subject: Re: [Qemu-devel] [PATCH v1 00/13] Fix VNC server unbounded memory usage
Date: Tue, 19 Dec 2017 09:57:59 -0500 (EST)


----- Original Message -----
> In the 2.11 release we fixed CVE-2017-15268, which allowed the VNC websockets
> server to consume arbitrary memory when a slow client was connected. I have
> since discovered that this same type of problem can be triggered in several
> other ways in the regular (non-websockets) VNC server. This patch series
> attempts to fix this problem by limiting framebuffer updates and other data
> sent from server to client. The mitigating factor is that you need to have
> successfully authenticated with the VNC server to trigger these new flaws.
> This new more general flaw is assigned CVE-2017-15124 by the Red Hat security
> team.
> The key patches containing the security fix are 9, 10, 11.
> Since this code is incredibly subtle & hard to understand though, the first
> 8 patches do a bunch of independant cleanups/refactoring to make the security
> fixes clearer.  The last two patches are just some extra cleanup / help for
> future maint.

I already reviewed the series privately, and in general, I'd ack it.

Did you manage to run some throttle tests? (I tried to trigger them manually by 
slowing artificially network or calling framebuffer_update_request() in gdb, I 
didn't manage yet :-/)

> Daniel P. Berrange (13):
>   ui: remove 'sync' parametr from vnc_update_client
>   ui: remove unreachable code in vnc_update_client
>   ui: remove redundant indentation in vnc_client_update
>   ui: avoid pointless VNC updates if framebuffer isn't dirty
>   ui: track how much decoded data we consumed when doing SASL encoding
>   ui: introduce enum to track VNC client framebuffer update request
>     state
>   ui: correctly reset framebuffer update state after processing dirty
>     regions
>   ui: refactor code for determining if an update should be sent to the
>     client
>   ui: fix VNC client throttling when audio capture is active
>   ui: fix VNC client throttling when forced update is requested
>   ui: place a hard cap on VNC server output buffer size
>   ui: add trace events related to VNC client throttling
>   ui: mix misleading comments & return types of VNC I/O helper methods
>  ui/trace-events    |   7 ++
>  ui/vnc-auth-sasl.c |  16 ++-
>  ui/vnc-auth-sasl.h |   5 +-
>  ui/vnc-jobs.c      |   5 +
>  ui/vnc.c           | 320
>  ++++++++++++++++++++++++++++++++++++++---------------
>  ui/vnc.h           |  28 ++++-
>  6 files changed, 277 insertions(+), 104 deletions(-)

Reviewed-by: Marc-André Lureau <address@hidden>

> --
> 2.14.3

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