Date: Mon, 16 Oct 2017 13:04:22 -0400 From: Jonathan Looney <jonlooney@gmail.com> To: Julien Charbon <jch@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r324179 - head/sys/netinet Message-ID: <CADrOrmvRTRim3DaD01ZKOrNRrfCq7GKqtFqsxsV-yCRvAppLvA@mail.gmail.com> In-Reply-To: <201710012120.v91LKSH1050145@repo.freebsd.org> References: <201710012120.v91LKSH1050145@repo.freebsd.org>
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Hi Julien, I apologize for just getting to this, but your code just made it into my local tree. The non-INVARIANTS case looks incorrect. Because tw stays on the list, it can end up stuck at the front of the queue and block everything behind it. Personally, I would be more comfortable just panic'ing here. This indicates a problem. And, depending on the way things got corrupted, you could end up with other hard-to-debug problems if you continue with a corrupted state. Jonathan On Sun, Oct 1, 2017 at 5:20 PM, Julien Charbon <jch@freebsd.org> wrote: > Author: jch > Date: Sun Oct 1 21:20:28 2017 > New Revision: 324179 > URL: https://svnweb.freebsd.org/changeset/base/324179 > > Log: > Fix an infinite loop in tcp_tw_2msl_scan() when an INP_TIMEWAIT inp has > been destroyed before its tcptw with INVARIANTS undefined. > > This is a symmetric change of r307551: > > A INP_TIMEWAIT inp should not be destroyed before its tcptw, and > INVARIANTS > will catch this case. If INVARIANTS is undefined it will emit a > log(LOG_ERR) > and avoid a hard to debug infinite loop in tcp_tw_2msl_scan(). > > Reported by: Ben Rubson, hselasky > Submitted by: hselasky > Tested by: Ben Rubson, jch > MFC after: 1 week > Sponsored by: Verisign, inc > Differential Revision: https://reviews.freebsd.org/D12267 > > Modified: > head/sys/netinet/tcp_timewait.c > > Modified: head/sys/netinet/tcp_timewait.c > ============================================================ > ================== > --- head/sys/netinet/tcp_timewait.c Sun Oct 1 20:12:30 2017 > (r324178) > +++ head/sys/netinet/tcp_timewait.c Sun Oct 1 21:20:28 2017 > (r324179) > @@ -709,10 +709,29 @@ tcp_tw_2msl_scan(int reuse) > INP_WLOCK(inp); > tw = intotw(inp); > if (in_pcbrele_wlocked(inp)) { > - KASSERT(tw == NULL, ("%s: held last inp " > - "reference but tw not NULL", > __func__)); > - INP_INFO_RUNLOCK(&V_tcbinfo); > - continue; > + if (__predict_true(tw == NULL)) { > + INP_INFO_RUNLOCK(&V_tcbinfo); > + continue; > + } else { > + /* This should not happen as in > TIMEWAIT > + * state the inp should not be > destroyed > + * before its tcptw. If INVARIANTS > is > + * defined panic. > + */ > +#ifdef INVARIANTS > + panic("%s: Panic before an > infinite " > + "loop: INP_TIMEWAIT && > (INP_FREED " > + "|| inp last reference) && tw > != " > + "NULL", __func__); > +#else > + log(LOG_ERR, "%s: Avoid an > infinite " > + "loop: INP_TIMEWAIT && > (INP_FREED " > + "|| inp last reference) && tw > != " > + "NULL", __func__); > +#endif > + INP_INFO_RUNLOCK(&V_tcbinfo); > + break; > + } > } > > if (tw == NULL) { > >
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