Date: Fri, 5 Jul 2013 14:30:54 +0000 (UTC) From: Andre Oppermann <andre@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r252787 - stable/9/sys/netinet Message-ID: <201307051430.r65EUs2S059154@svn.freebsd.org>
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Author: andre Date: Fri Jul 5 14:30:54 2013 New Revision: 252787 URL: http://svnweb.freebsd.org/changeset/base/252787 Log: MFC r249317: Fix a race condition on tcp listen socket teardown with pending connections in the accept queue and contiguous new incoming SYNs. Compared to the original submitters patch I've moved the test next to the SYN handling to have it together in a logical unit and reworded the comment explaining the issue. Submitted by: Matt Miller <matt@matthewjmiller.net> Submitted by: Juan Mojica <jmojica@gmail.com> Reviewed by: Matt Miller (changes) Tested by: pho Modified: stable/9/sys/netinet/tcp_input.c Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/netinet/tcp_input.c ============================================================================== --- stable/9/sys/netinet/tcp_input.c Fri Jul 5 14:24:37 2013 (r252786) +++ stable/9/sys/netinet/tcp_input.c Fri Jul 5 14:30:54 2013 (r252787) @@ -1375,6 +1375,15 @@ relocked: */ INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); return; + } else if (tp->t_state == TCPS_LISTEN) { + /* + * When a listen socket is torn down the SO_ACCEPTCONN + * flag is removed first while connections are drained + * from the accept queue in a unlock/lock cycle of the + * ACCEPT_LOCK, opening a race condition allowing a SYN + * attempt go through unhandled. + */ + goto dropunlock; } #ifdef TCP_SIGNATURE
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