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Bug 1400422

Summary: Use-after free in resolver in case the fd is writeable and readable at the same time
Product: Red Hat Enterprise Linux 7 Reporter: Jakub Hrozek <jhrozek>
Component: sssdAssignee: SSSD Maintainers <sssd-maint>
Status: CLOSED ERRATA QA Contact: Amith <apeetham>
Severity: urgent Docs Contact:
Priority: urgent    
Version: 7.3CC: ekeck, grajaiya, hkhot, jhrozek, lslebodn, mkosek, mzidek, nsoman, orion, pbrezina, sgoveas, tscherf
Target Milestone: rcKeywords: ZStream
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: sssd-1.15.0-1.el7 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
: 1404340 (view as bug list) Environment:
Last Closed: 2017-08-01 09:02:33 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1404340    
Attachments:
Description Flags
core_backtrace none

Description Jakub Hrozek 2016-12-01 08:02:45 UTC
This bug is created as a clone of upstream ticket:
https://fedorahosted.org/sssd/ticket/3250

Carl Henrik Holth Lunde found a bug in SSSD resolver code in case the file descriptor we use to integrate c-ares with libtevent is both readable and writable at the same time. In this case, we process the request twice, both for TEVENT_FD_WRITE and TEVENT_FD_READ. The first callback processing frees the internal watch structure and the second callback invocation accesses invalid memory.

Carl also proposed a patch for this bug himself.

Comment 1 Jakub Hrozek 2016-12-01 08:05:39 UTC
There is no reliable reproducer. For testing, I would recommend to run our regression tests for the resolver and the fail over code.

Comment 2 Jakub Hrozek 2016-12-02 10:26:24 UTC
Hi Namita,
could you please qa_ack this bug in Steeve's absence this week? See comment #1 about reproducer.

The customer impact is an intermittent crash in their environment and because we are already planning a 7.3 z-stream update, I would like to include this bug as well.

Thank you!

Comment 3 Jakub Hrozek 2016-12-08 10:58:09 UTC
Fixed upstream:
    master: 9676b464dd428557ff5a648e1351a3972440396f
    sssd-1-14: fefdd70237cbe82af7d8845131e45401e73b3b07
    sssd-1-13: 07959a61f12cd9e60dff6651f4e1ce05c83c4da7

Comment 4 Jakub Hrozek 2016-12-13 14:23:29 UTC
Hi Thorsten, could you please add GSSApproved for this bug? It's a crasher for the customer and a fix is available..

Comment 8 Orion Poplawski 2017-05-04 17:08:11 UTC
Created attachment 1276398 [details]
core_backtrace

Is this the same crash?  Can't find a backtrace in either bug report so hard to tell.

Comment 9 Jakub Hrozek 2017-05-04 19:07:09 UTC
(In reply to Orion Poplawski from comment #8)
> Created attachment 1276398 [details]
> core_backtrace
> 
> Is this the same crash?  Can't find a backtrace in either bug report so hard
> to tell.

No, I'm afraid yours is a different issue, because the backtrace of this bug would be (judging by commit message of its fix):
    Invalid read of size 4
       at fd_input_available (async_resolv.c:147)
       by epoll_event_loop (tevent_epoll.c:728)
       by epoll_event_loop_once (tevent_epoll.c:926)
       by std_event_loop_once (tevent_standard.c:114)
       by _tevent_loop_once (tevent.c:533)
       by tevent_common_loop_wait (tevent.c:637)
       by std_event_loop_wait (tevent_standard.c:140)
       by server_loop (server.c:702)
       by main (data_provider_be.c:587)

Yours goes through sss_ldap_init_send

Comment 10 Lukas Slebodnik 2017-05-05 08:35:50 UTC
Orion,
Please file a new bug.

Comment 11 Amith 2017-05-18 03:21:20 UTC
Verified Sanity only on SSSD Version: sssd-1.15.2-29.el7.x86_64

The automated regression round for the FAILOVER suite which covers the resolver code as well, was executed successfully on beaker.

See beaker job: https://beaker.engineering.redhat.com/jobs/1860966

Comment 12 errata-xmlrpc 2017-08-01 09:02:33 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2017:2294

Comment 13 Alexey Tikhonov 2020-11-04 11:58:13 UTC
*** Bug 1894237 has been marked as a duplicate of this bug. ***