[ovs-dev] [PATCHv2] connmgr: Check nullptr inside ofmonitor_report()

[贺鹏]

Hi,

Looks like this bug is caused by violating the fact that if a rule is
referenced, the related ofproto should not be destroyed.

If so, I have a patch that also fixes the problem, not sure if this helps.

http://patchwork.ozlabs.org/project/openvswitch/patch/20200717015041.82746-1-hepeng.0320@bytedance.com/

William Tu <u9012063 at gmail.com> 于2021年2月19日周五 上午8:10写道：
>
> On Wed, Feb 17, 2021 at 1:09 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.
> >
> > 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>
> > ---
> > v1->v2: Add check for ofmonitor_flush, thanks William.
> >
>
> LGTM, thanks.
> Acked-by: William Tu < u9012063 at gmail.com>
>
> CC Ilya and Ben to see if any comments.
>
> I feel this kind of RCU issue is hard to find out, and
> existing tools such as addressSanitizer are usually
> not helpful.
>
> William
>
> >  ofproto/connmgr.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/ofproto/connmgr.c b/ofproto/connmgr.c
> > index 9c5c633b4171..fa8f6cd0e83a 100644
> > --- a/ofproto/connmgr.c
> > +++ b/ofproto/connmgr.c
> > @@ -2140,7 +2140,7 @@ ofmonitor_report(struct connmgr *mgr, struct rule *rule,
> >                   const struct rule_actions *old_actions)
> >      OVS_REQUIRES(ofproto_mutex)
> >  {
> > -    if (rule_is_hidden(rule)) {
> > +    if (!mgr || rule_is_hidden(rule)) {
> >          return;
> >      }
> >
> > @@ -2244,6 +2244,10 @@ ofmonitor_flush(struct connmgr *mgr)
> >  {
> >      struct ofconn *ofconn;
> >
> > +    if (!mgr) {
> > +        return;
> > +    }
> > +
> >      LIST_FOR_EACH (ofconn, connmgr_node, &mgr->conns) {
> >          struct rconn_packet_counter *counter = ofconn->monitor_counter;
> >
> > --
> > 2.7.4
> >
> > _______________________________________________
> > dev mailing list
> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
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-- 
hepeng