[1/6] af_unix: limit unix_tot_inflight CVE-2010-4249

From: Eric Dumazet <eric.dumazet@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@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
---
 net/unix/garbage.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

Matches the upstream commit. But seems to miss reference.

On 04.07.2011 11:53, paolo.pisati@canonical.com wrote:
> From: Eric Dumazet <eric.dumazet@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@gmail.com>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>

(cherry-picked from 9915672d41273f5b77f1b3c29b391ffb7732b84b upstream)
> Signed-off-by: Brad Figg <brad.figg@canonical.com>
> Signed-off-by: Paolo Pisati <paolo.pisati@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 07499a5..dc2cb61 100644
> --- a/net/unix/garbage.c
> +++ b/net/unix/garbage.c
> @@ -269,9 +269,16 @@ static void inc_inflight_move_tail(struct unix_sock *u)
>  }
>  
>  static bool gc_in_progress = false;
> +#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 (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress)
> +		unix_gc();
>  	wait_event(unix_gc_wait, gc_in_progress == false);
>  }
>  

Otherwise

Acked-by: Stefan Bader <stefan.bader@canonical.com>