CVS commit: [netbsd-8] src/sys/net

["Martin Husemann" <martin%netbsd.org@localhost>]

Module Name:    src
Committed By:   martin
Date:           Thu Jul 12 15:11:56 UTC 2018

Modified Files:
        src/sys/net [netbsd-8]: if_pppoe.c

Log Message:
Pull up following revision(s) (requested by yamaguchi in ticket #890):
        sys/net/if_pppoe.c: revision 1.137
        sys/net/if_pppoe.c: revision 1.139
        sys/net/if_pppoe.c: revision 1.140
Drop early if there's no PPPoE interface. Otherwise it is easy for someone
to flood dmesg over the local subnet.
Fix not to use PPPOE_UNLOCK before acccess to pppoe_softc
to avoid a race condition
According to the locking order of pppoe(4), the access to
pppoe_softc has to follow 5 steps as below.
1. aquire pppoe_softc_list_lock
2. aquire pppoe_softc lock
3. release pppoe_softc_list_lock
4. access to pppoe_softc
5. release pppoe_softc lock
However, pppoe_dispatch_disc_pkt() releases the lock of pppoe_softc
temporarily, and then re-aquires it before step 4 of the adove. So,
it is possible for other contexts to destroy a pppoe_softc in the
interim.
To fix this condition, avoid PPPOE_UNLOCK with the problem.
ok by knakahara@n.o
Fix to aquire pppoe_softc_list_lock before read and write the list
ok by knakahara@n.o


To generate a diff of this commit:
cvs rdiff -u -r1.125.6.8 -r1.125.6.9 src/sys/net/if_pppoe.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.