From 6034a281f077b621859fb7b2f362fc9d693ea218 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 24 Nov 2010 09:15:27 -0800 Subject: [PATCH] af_unix: limit unix_tot_inflight commit 9915672d41273f5b77f1b3c29b391ffb7732b84b upstream. 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 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/unix/garbage.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/unix/garbage.c b/net/unix/garbage.c index 97d1a380423c..cb72e91f1489 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); } -- 2.39.5