[Dapper] [CVE-2010-4249] [PATCH 1/1] af_unix: limit unix_tot_inflight, CVE-2010-4249

Tim Gardner tim.gardner at canonical.com
Sat Apr 23 12:52:51 UTC 2011


On 04/22/2011 02:47 PM, Brad Figg wrote:
> From: Eric Dumazet<eric.dumazet at gmail.com>
>
> CVE-2010-4249
>
> BugLink: http://bugs.launchpad.net/bugs/769182
>
> Vegard Nossum found a unix socket OOM was possible, posting an exploit
> program.
>
> My analysis is we can eat all LOWMEM memory before unix_gc() being
> called from unix_release_sock(). Moreover, the thread blocked in
> unix_gc() can consume huge amount of time to perform cleanup because of
> huge working set.
>
> One way to handle this is to have a sensible limit on unix_tot_inflight,
> tested from wait_for_unix_gc() and to force a call to unix_gc() if this
> limit is hit.
>
> This solves the OOM and also reduce overall latencies, and should not
> slowdown normal workloads.
>
> Reported-by: Vegard Nossum<vegard.nossum at gmail.com>
> Signed-off-by: Eric Dumazet<eric.dumazet at gmail.com>
> Signed-off-by: David S. Miller<davem at davemloft.net>
> Signed-off-by: Brad Figg<brad.figg at canonical.com>
> ---
>   net/unix/garbage.c |    7 +++++++
>   1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/net/unix/garbage.c b/net/unix/garbage.c
> index 040f952..26d22aa 100644
> --- a/net/unix/garbage.c
> +++ b/net/unix/garbage.c
> @@ -168,9 +168,16 @@ static void maybe_unmark_and_push(struct sock *x)
>
>
>   static int gc_in_progress = 0;
> +#define UNIX_INFLIGHT_TRIGGER_GC 16000
>
>   void wait_for_unix_gc(void)
>   {
> +	/*
> +	 * If number of inflight sockets is insane,
> +	 * force a garbage collect right now.
> +	 */
> +	if (atomic_read(&unix_tot_inflight)>  UNIX_INFLIGHT_TRIGGER_GC&&  !gc_in_progress)
> +		unix_gc();
>   	wait_event(unix_gc_wait, gc_in_progress == 0);
>   }
>

Looks reasonable. Was this a clean cherry-pick, or a backport ?

Acked-by: Tim Gardner <tim.gardner at canonical.com>

-- 
Tim Gardner tim.gardner at canonical.com



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