Ubuntu
unscd package

unscd segfaults regularly

Bug #1376274 reported by Tamas Papp on 2014-10-01

This bug affects 4 people

Affects		Status	Importance	Assigned to	Milestone
	unscd (Ubuntu)	Fix Released	Medium	Bryan Quigley
	Trusty	Fix Released	Medium	Unassigned

Bug Description

[Impact]

* It's causing a crash.

[Test Case]

* detailed instructions how to reproduce the bug

[Regression Potential]

* The fix just checks for one NULL pointer, and it's been in 16.04 and above since release, per comment #3.

Original Report:
kern.log:Oct 1 11:34:51 camel kernel: [1715974.313870] nscd[11501]: segfault at 0 ip 0000000000403b71 sp 00007fff8ba4def0 error 4 in nscd[400000+8000]

unscd is getting died after a not very long time.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: unscd 0.51-1build2
ProcVersionSignature: Ubuntu 3.13.0-35.62-generic 3.13.11.6
Uname: Linux 3.13.0-35-generic x86_64
NonfreeKernelModules: vhost_net vhost macvtap macvlan ipt_MASQUERADE iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle xt_tcpudp ip6table_filter ip6_tables iptable_filter ip_tables x_tables veth bridge stp llc gpio_ich x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd sb_edac joydev edac_core mei_me mei lpc_ich ipmi_si wmi ioatdma mac_hid lp parport zfs zunicode zavl zcommon znvpair spl btrfs libcrc32c raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor igb raid6_pq i2c_algo_bit raid1 isci mpt2sas hid_generic dca raid0 libsas usbhid raid_class ptp ahci multipath hid libahci scsi_transport_sas pps_core linear
ApportVersion: 2.14.1-0ubuntu3.4
Architecture: amd64
Date: Wed Oct 1 15:49:48 2014
Dependencies:
gcc-4.9-base 4.9.1-0ubuntu1
libc6 2.19-0ubuntu6.3
libgcc1 1:4.9.1-0ubuntu1
multiarch-support 2.19-0ubuntu6.3
SourcePackage: unscd
UpgradeStatus: Upgraded to trusty on 2014-06-04 (119 days ago)

See original description

Tags:

Revision history for this message

Tamas Papp (tomposmiko) wrote on 2014-10-01:

ProcEnviron.txt Edit (297 bytes, text/plain; charset="utf-8")

Revision history for this message

Launchpad Janitor (janitor) wrote on 2016-03-01:

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in unscd (Ubuntu):
status:	New → Confirmed

Florian Klemenz (klelifo) on 2016-03-01

summary:

- unscd segfault
+ unscd segfaults regularly

Revision history for this message

Florian Klemenz (klelifo) wrote on 2016-03-01:

valgrind.log Edit (39.8 KiB, text/plain)

I have the same problem.
After starting unscd it segfaults after a short time.
If many requests occur virtually immediatly.

The attached output of valgrind supports this claim:
valgrind -v --leak-check=full --show-leak-kinds=all --trace-children=yes nscd -d 2>&1 | tee /tmp/valgrind.log

...
==2487== Process terminating with default action of signal 11 (SIGSEGV)
==2487== Access not within mapped region at address 0x0
==2487== at 0x403B71: free_refcounted_ureq (nscd.c:1220)
==2487== by 0x403C72: close_client (nscd.c:808)
==2487== by 0x402544: handle_client (nscd.c:1602)
==2487== by 0x402544: main_loop (nscd.c:2027)
==2487== by 0x402544: main (nscd.c:2654)
...

This points to line 1220 in nscd.c as the source of the problem.
Problem appears to be fixed in unscd_0.52-1 (there was a NULL check added at exactly this code position).
Also installing a manually build package of unscd_0.52-1 fixes the problem.

Obvious resolution would be to provide an official unscd_0.52-1 package for 14.04

Revision history for this message

Patrik Martinsson (patrik.martinsson) wrote on 2016-03-07:

Hi,

I can confirm this behavior on all our servers running ubuntu 14.04.
If we are going to continue to use uncsd, we really need this fix backported to 14.04.

I'm new here, but who decides if this is going to be fixed in 14.04 or not ?
And when is that decision being made ?

Best regards,
Patrik Martinsson,
Sweden

Revision history for this message

Tamas Papp (tomposmiko) wrote on 2016-03-07:

You better switch to sssd.

Revision history for this message

Scott Moser (smoser) wrote on 2016-10-25:

Tamas,
Please correct me if I'm wrong, but it does not look to me like sssd supports dns/hosts caching.

Bryan Quigley (bryanquigley) on 2016-10-27

Changed in unscd (Ubuntu):
assignee:	nobody → Bryan Quigley (bryanquigley)

Revision history for this message

Bryan Quigley (bryanquigley) wrote on 2016-10-27:

unscd_0.51-1ubuntu1.debdiff Edit (2.1 KiB, text/plain)

Here is a debdiff that backports the single NULL check (which is all of 0.52) to Trusty.

Revision history for this message

Bryan Quigley (bryanquigley) wrote on 2016-10-27:

I've created a debdiff to backport the fix to 14.04. We could use more details on both the impact and a step-by-step way (from a fresh cloud image) to reproduce the bug.

description:

updated

Revision history for this message

Ubuntu Foundations Team Bug Bot (crichton) wrote on 2016-10-27:

The attachment "unscd_0.51-1ubuntu1.debdiff" seems to be a debdiff. The ubuntu-sponsors team has been subscribed to the bug report so that they can review and hopefully sponsor the debdiff. If the attachment isn't a patch, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are member of the ~ubuntu-sponsors, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issue please contact him.]

tags:

added: patch

Mathew Hodson (mhodson) on 2016-10-28

Changed in unscd (Ubuntu):
importance:	Undecided → Medium

Jeremy Bícha (jbicha) on 2016-10-29

Changed in unscd (Ubuntu):
status:	Confirmed → Fix Released
Changed in unscd (Ubuntu Trusty):
importance:	Undecided → Medium
status:	New → Triaged

Revision history for this message

Daniel Holbach (dholbach) wrote on 2016-11-01:

#10

I uploaded the change. Can you please add a test-case for the ubuntu-sru team to the description to the bug?

Changed in unscd (Ubuntu Trusty):
status:	Triaged → Fix Committed

Revision history for this message

Bryan Quigley (bryanquigley) wrote on 2016-11-01:

#11

Thanks Daniel!

I unfortunately don't have a test case. Anyone else who has this bug, please provide one so we can get this fixed.

Revision history for this message

Sebastien Bacher (seb128) wrote on 2016-11-08:

#12

the debdiff has been uploaded, unsubscribing the sponsors

Revision history for this message

Brian Murray (brian-murray) wrote on 2016-11-10: Please test proposed package

#13

Hello Tamas, or anyone else affected,

Accepted unscd into trusty-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/unscd/0.51-1ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

tags:

added: verification-needed

Revision history for this message

Ubuntu Foundations Team Bug Bot (crichton) wrote on 2017-02-09: [unscd/trusty] verification still needed

#14

The fix for this bug has been awaiting testing feedback in the -proposed repository for trusty for more than 90 days. Please test this fix and update the bug appropriately with the results. In the event that the fix for this bug is still not verified 15 days from now, the package will be removed from the -proposed repository.

tags:

added: removal-candidate

Revision history for this message

Tamas Papp (tomposmiko) wrote on 2017-02-10:

#15

Sorry, I have already switched to sssd, cannot test the fix.

Revision history for this message

Bryan Quigley (bryanquigley) wrote on 2017-02-23:

#16

I've asked for testing privately with no luck. I think this will have to be removed.

Revision history for this message

Stephen A. Zarkos (stevez) wrote on 2017-02-23:

#17

I've tested unscd with the patch and saw no issues, but unfortunately there is no simple repro script that generates the failure. Customers just see this issue appear after some time of running the service.

The customer in comment #3 also confirmed that unscd_0.52-1 fixes the issue for them, and this null pointer check is the only change in that release. To me this seems low risk to keep the null pointer check and release this.

tags:

added: verification-done
removed: verification-needed

Revision history for this message

Launchpad Janitor (janitor) wrote on 2017-02-27:

#18

This bug was fixed in the package unscd - 0.51-1ubuntu1

---------------
unscd (0.51-1ubuntu1) trusty-proposed; urgency=medium

* Backport of full 0.52 release which just contains one NULL
pointer check. (LP: #1376274)

-- Bryan Quigley <email address hidden> Thu, 27 Oct 2016 18:44:09 +0000

Changed in unscd (Ubuntu Trusty):
status:	Fix Committed → Fix Released

Revision history for this message

Brian Murray (brian-murray) wrote on 2017-02-27: Update Released

#19

The verification of the Stable Release Update for unscd has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.