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af_unix: limit unix_tot_inflight

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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>
This commit is contained in:
Eric Dumazet 2010-11-24 09:15:27 -08:00 committed by David S. Miller
parent cf41a51db8
commit 9915672d41
1 changed files with 7 additions and 0 deletions
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7
net/unix/garbage.c
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@ -259,9 +259,16 @@ 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);
}