Date: Sat, 08 Dec 2012 10:13:45 -0800 From: Richard Sharpe <rsharpe@richardsharpe.com> To: freebsd-hackers@freebsd.org Subject: Possible obscure socket leak when system under load and listener is slow to accept Message-ID: <1354990425.6752.10.camel@localhost.localdomain>
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Hi folks,
Our QA group (at xxx) using Samba and smbtorture has been seeing a
lot of cases where accept returns ECONNABORTED because the system load
is high and Samba has a large listen backlog.
Every now and then we get a crash in smbd or in winbindd and winbindd
complains of too many open files in the system.
In looking at kern_accept, it seems to me that FreeBSD can leak a socket
when kern_accept calls soaccept on it but gets ECONNABORTED. This error
is the only error returned from tcp_usr_accept.
It seems like the socket taken off so_comp is never freed in this case
and that there has been a call on soref on it as well, so that something
like the following is needed in the error path:
==== //some-path/freebsd/sys/kern/uipc_syscalls.c#1
- /home/rsharpe/dev-src/packages/freebsd/sys/kern/uipc_syscalls.c ====
@@ -433,6 +433,14 @@
*/
if (name)
*namelen = 0;
+ /*
+ * We need to close the socket we unlinked
+ * so we do not leak it.
+ */
+ ACCEPT_LOCK();
+ SOCK_LOCK(so);
+ soclose(so);
goto noconnection;
}
if (sa == NULL) {
I think an soclose is needed at this point because soisconnected has
been called on the socket.
Do you think this analysis is reasonable?
We are using FreeBSD 8.0 but it seems the same is true for 9.0. However,
maybe I am wrong since I am not sure if the fdclose call would free the
socket, but a quick look suggested that it doesn't.
I would appreciate your feedback.
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