git: AF_UNIX: Hold a reference of the unp_conn before executing blocking code

[Sepherosa Ziehau <sephe@xxxxxxxxxxxxxxxxxxxxxxx>]

commit 76d4bfa31c73732ae74b63f8fe1cbdc9d8df7a52
Author: Sepherosa Ziehau <sephe@dragonflybsd.org>
Date:   Wed Apr 27 15:10:03 2011 +0800

    AF_UNIX: Hold a reference of the unp_conn before executing blocking code
    
    Since unp_token will be automaticly released upon execution of blocking
    code, close of unp_conn could race any code paths that references unp_conn
    after executing blocking code.  To fix these races, we simply increment
    the reference count of the unp_conn before executig any possibly blocking
    code and release the reference count of unp_conn, which may release unp_conn
    itself.  This _currently_ does not suffer 0-ref race, since unp_token is
    always being held.

Summary of changes:
 sys/kern/uipc_usrreq.c |   77 ++++++++++++++++++++++++++++++++++++++++-------
 sys/sys/unpcb.h        |    2 +-
 2 files changed, 66 insertions(+), 13 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/76d4bfa31c73732ae74b63f8fe1cbdc9d8df7a52


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