[ovs-dev] [PATCH] connmgr: Check nullptr inside ofmonitor_report()

Yifeng Sun pkusunyifeng at gmail.com
Wed Feb 17 21:09:54 UTC 2021


Thanks William and YiHung for review, I sent a new version.

On Tue, Feb 16, 2021 at 8:45 PM William Tu <u9012063 at gmail.com> wrote:

> On Tue, Feb 16, 2021 at 1:40 PM Yi-Hung Wei <yihung.wei at gmail.com> wrote:
> >
> > On Tue, Feb 16, 2021 at 1:06 PM Yifeng Sun <pkusunyifeng at gmail.com>
> wrote:
> > >
> > > ovs-vswitchd could crash under these circumstances:
> > > 1. When one bridge is being destroyed, ofproto_destroy() is called and
> > > connmgr pointer of its ofproto struct is nullified. This ofproto
> struct is
> > > deallocated through 'ovsrcu_postpone(ofproto_destroy_defer__, p);'.
> > > 2. Before RCU enters quiesce state to actually free this ofproto
> struct,
> > > revalidator thread calls udpif_revalidator(), which could handle
> > > a learn flow and calls ofproto_flow_mod_learn(), it later calls
> > > ofmonitor_report() and ofproto struct's connmgr pointer is accessed.
> > >
>
> LGTM, thanks. I guess this is hard to reproduce or create a test.
> Do we need to worry about other places that use 'ofproto->connmgr'?
> ex: there are a couple of places calling ofmonitor_flush(ofproto->connmgr);
>
> > > The crash stack trace is shown below:
> > >
> > > 0  ofmonitor_report (mgr=0x0, rule=rule at entry=0x7fa4ac067c30,
> event=event at entry=NXFME_ADDED,
> > >     reason=reason at entry=OFPRR_IDLE_TIMEOUT, abbrev_ofconn=0x0,
> abbrev_xid=0, old_actions=old_actions at entry=0x0)
> > >     at ofproto/connmgr.c:2160
> > > 1  0x00007fa4d6803495 in add_flow_finish (ofproto=0x55d9075d4ab0,
> ofm=<optimized out>, req=req at entry=0x0)
> > >     at ofproto/ofproto.c:5221
> > > 2  0x00007fa4d68036af in modify_flows_finish (req=0x0,
> ofm=0x7fa4980753f0, ofproto=0x55d9075d4ab0)
> > >     at ofproto/ofproto.c:5823
> > > 3  ofproto_flow_mod_finish (ofproto=0x55d9075d4ab0, ofm=ofm at entry=0x7fa4980753f0,
> req=req at entry=0x0)
> > >     at ofproto/ofproto.c:8088
> > > 4  0x00007fa4d680372d in ofproto_flow_mod_learn_finish (ofm=ofm at entry
> =0x7fa4980753f0,
> > >     orig_ofproto=orig_ofproto at entry=0x0) at ofproto/ofproto.c:5439
> > > 5  0x00007fa4d68072f9 in ofproto_flow_mod_learn (ofm=0x7fa4980753f0,
> keep_ref=keep_ref at entry=true,
> > >     limit=<optimized out>, below_limitp=below_limitp at entry=0x0) at
> ofproto/ofproto.c:5499
> > > 6  0x00007fa4d6835d33 in xlate_push_stats_entry (entry=0x7fa498012448,
> stats=stats at entry=0x7fa4d2701a10,
> > >     offloaded=offloaded at entry=false) at
> ofproto/ofproto-dpif-xlate-cache.c:127
> > > 7  0x00007fa4d6835e3a in xlate_push_stats (xcache=<optimized out>,
> stats=stats at entry=0x7fa4d2701a10,
> > >     offloaded=offloaded at entry=false) at
> ofproto/ofproto-dpif-xlate-cache.c:181
> > > 8  0x00007fa4d6822046 in revalidate_ukey (udpif=udpif at entry=0x55d90760b240,
> ukey=ukey at entry=0x7fa4b0191660,
> > >     stats=stats at entry=0x7fa4d2705118, odp_actions=odp_actions at entry
> =0x7fa4d2701b50,
> > >     reval_seq=reval_seq at entry=5655486242, recircs=recircs at entry=0x7fa4d2701b40,
> offloaded=false)
> > >     at ofproto/ofproto-dpif-upcall.c:2294
> > > 9  0x00007fa4d6825aee in revalidate (revalidator=0x55d90769dd00) at
> ofproto/ofproto-dpif-upcall.c:2683
> > > 10 0x00007fa4d6825cf3 in udpif_revalidator (arg=0x55d90769dd00) at
> ofproto/ofproto-dpif-upcall.c:936
> > > 11 0x00007fa4d6259c9f in ovsthread_wrapper (aux_=<optimized out>) at
> lib/ovs-thread.c:423
> > > 12 0x00007fa4d582cea5 in start_thread () from
> /usr/lib64/libpthread.so.0
> > > 13 0x00007fa4d504b96d in clone () from /usr/lib64/libc.so.6
> > >
> > > At the time of crash, the involved ofproto was already deallocated:
> > >
> > > (gdb) print *ofproto
> > > $1 = ..., name = 0x55d907602820 "nsx-managed", ..., ports = {...,
> > >     one = 0x0, mask = 63, n = 0}, ..., connmgr = 0x0, ...
> > >
> > > This patch fixes it.
> > >
> > > VMware-BZ: #2700626
> > > Signed-off-by: Yifeng Sun <pkusunyifeng at gmail.com>
> > > ---
> >
> > LGTM.
> >
> > Acked-by: Yi-Hung Wei <yihung.wei at gmail.com>
> > _______________________________________________
> > dev mailing list
> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
>


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