Date: Sat, 6 Mar 2010 21:38:31 +0000 (UTC) From: Robert Watson <rwatson@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r204809 - head/sys/netinet Message-ID: <201003062138.o26LcVXU044632@svn.freebsd.org>
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Author: rwatson Date: Sat Mar 6 21:38:31 2010 New Revision: 204809 URL: http://svn.freebsd.org/changeset/base/204809 Log: Add a comment to tcp_usr_accept() to indicate why it is we acquire the tcbinfo lock there: r175612, which re-added it, masked a race between sonewconn(2) and accept(2) that could allow an incompletely initialized address on a newly-created socket on a listen queue to be exposed. Full details can be found in that commit message. MFC after: 1 week Sponsored by: Juniper Networks Modified: head/sys/netinet/tcp_usrreq.c Modified: head/sys/netinet/tcp_usrreq.c ============================================================================== --- head/sys/netinet/tcp_usrreq.c Sat Mar 6 21:27:26 2010 (r204808) +++ head/sys/netinet/tcp_usrreq.c Sat Mar 6 21:38:31 2010 (r204809) @@ -560,9 +560,15 @@ out: } /* - * Accept a connection. Essentially all the work is - * done at higher levels; just return the address - * of the peer, storing through addr. + * Accept a connection. Essentially all the work is done at higher levels; + * just return the address of the peer, storing through addr. + * + * The rationale for acquiring the tcbinfo lock here is somewhat complicated, + * and is described in detail in the commit log entry for r175612. Acquiring + * it delays an accept(2) racing with sonewconn(), which inserts the socket + * before the inpcb address/port fields are initialized. A better fix would + * prevent the socket from being placed in the listen queue until all fields + * are fully initialized. */ static int tcp_usr_accept(struct socket *so, struct sockaddr **nam)
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