[SSSD] [PATCH] Fix LOCAL domain lookups

Jakub Hrozek jhrozek at redhat.com
Wed Aug 15 13:56:38 UTC 2012


On Tue, Aug 14, 2012 at 01:38:15PM +0200, Pavel Březina wrote:
> On 08/13/2012 11:42 AM, Jakub Hrozek wrote:
> >On Mon, Aug 13, 2012 at 11:10:36AM +0200, Jakub Hrozek wrote:
> >>On Fri, Aug 10, 2012 at 09:26:49AM +0200, Pavel Březina wrote:
> >>>On 08/08/2012 04:24 PM, Jakub Hrozek wrote:
> >>>>On Wed, Aug 08, 2012 at 02:23:04PM +0200, Pavel Březina wrote:
> >>>>>This bug was probably introduced with the subdomain patches. The
> >>>>>problem was that sss_dp_get_domains_send() is called even for the local
> >>>>>provider. There are certainly many possible solutions of this issue. I
> >>>>>decided to modify sss_dp_issue_request() to call the callback
> >>>>>immediately if it is issued for local domain. This way, I believe, we
> >>>>>can avoid further problems with issuing request for local domains.
> >>>>
> >>>>I don't think this is the best solution.
> >>>>
> >>>>First, it leaves the check_provider of the per-domain structures we use
> >>>>in responders around while duplicating the same functionality in the DP.
> >>>>At the very least, the patch should remove the "check_provider" tests from
> >>>>the existing loops.
> >>>>
> >>>>What I think would be even better solution is to
> >>>>     1) in the RC just fix the subdomains code so that it shortcuts or
> >>>>     doesn't run at all for LOCAL lookups.
> >>>
> >>>Patch is attached.
> >>
> >>Thank you, this works for me.
> >>
> >>I'm seeing this warning when LOCAL users are enumerated (as opposed to a
> >>direct lookup):
> >>(Mon Aug 13 11:06:58 2012) [sssd[nss]] [setent_notify] (0x0010): BUG: a
> >>callback did not free its request. May leak memory
> >>
> >>Given that the LOCAL domain is mostly useful for testing right now, I've
> >>just filed a ticket:
> >>https://fedorahosted.org/sssd/ticket/1477
> >>
> >>Ack
> >
> >Nack, upon further testing. I'm seeing segfaults when looking up
> >non-LOCAL users:
> >
> >Core was generated by `/usr/libexec/sssd/sssd_nss -d 0x17f0'.
> >Program terminated with signal 11, Segmentation fault.
> >#0  0x000000000043acb1 in get_domains_next (req=0xf95ca0) at src/responder/common/responder_get_domains.c:124
> >124             tevent_req_post(req, info->rctx->ev);
> >Missing separate debuginfos, use: debuginfo-install nss-softokn-freebl-3.13.5-1.fc17.x86_64 openldap-2.4.31-3.fc17.x86_64
> >(gdb) bt
> >#0  0x000000000043acb1 in get_domains_next (req=0xf95ca0) at src/responder/common/responder_get_domains.c:124
> >#1  0x000000000043b461 in sss_dp_get_domains_callback (subreq=0xf968b0) at src/responder/common/responder_get_domains.c:215
> >#2  0x0000000000439dd4 in sss_dp_internal_get_done (pending=0xf944e0, ptr=0xf99220) at src/responder/common/responder_dp.c:731
> >#3  0x000000342fa0c42a in complete_pending_call_and_unlock (connection=connection at entry=0xf95e40, pending=0xf944e0, message=message at entry=0xf98a80) at dbus-connection.c:2308
> >#4  0x000000342fa0f5ea in dbus_connection_dispatch (connection=0xf95e40) at dbus-connection.c:4593
> >#5  0x0000000000460432 in sbus_dispatch (ev=0xf89390, te=0xf98bc0, tv=..., data=0xf979a0) at src/sbus/sssd_dbus_connection.c:104
> >#6  0x000000385b407600 in tevent_common_loop_timer_delay (ev=ev at entry=0xf89390) at ../tevent_timed.c:254
> >#7  0x000000385b406cac in std_event_loop_once (ev=0xf89390, location=<optimized out>) at ../tevent_standard.c:560
> >#8  0x000000385b403ed0 in _tevent_loop_once (ev=ev at entry=0xf89390, location=location at entry=0x492f97 "src/util/server.c:554") at ../tevent.c:506
> >#9  0x000000385b40405b in tevent_common_loop_wait (ev=0xf89390, location=0x492f97 "src/util/server.c:554") at ../tevent.c:607
> >#10 0x0000000000467bf4 in server_loop (main_ctx=0xf8a4a0) at src/util/server.c:554
> >#11 0x0000000000408d5c in main (argc=3, argv=0x7fff2dde9cc8) at src/responder/nss/nsssrv.c:422
> >(gdb) p *info
> >$1 = {rctx = 0x3133623833347830, dom = 0x306d61736c3a313a, hint = 0x696e403334346336 <Address 0x696e403334346336 out of bounds>, force = 114, state = 0x0}
> >
> >It looks like "info" was not initialized.
> 
> Thanks.
> 
> The problem was that callback is invoked immediately when
> tevent_req_done() is called. And because req is freed in this
> callback, info was pointing to invalid data.
> 
> New patch is attached.

I think it would be much cleaner to remove the tevent_req_post
completely from get_domains_next() and only call it in
sss_dp_get_domains_send() if get_domains_next() returned EOK.

I wouldn't expect tevent_req_post to be called in any other function
that *_send. Also checking the SSSD code shows that we only call
tevent_req_post from *_send elsewhere.



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