Fix undefined behavior in TSGFromL2 from empty pointer

[CeliaFernandez]

PR description:

Fix undefined behavior in TSGFromL2Muon, reported in issue 35036. The issue is caused by the region pointer, which is only initialized if there is a valid theRegionBuilder in the event. The region pointer is then accessed empty in lines 102/104 and 106/108 when given as an input to trackerSeeds() and clean() functions.

To solve this issue, I added a default constructor without parameters for RectangularEtaPhiTrackingRegion and TrackingRegion classes. This makes possible to have a minimal initialization for the region pointer. The default initialization of region is done if theRegionBuilder states to false by adding an else statement in line 93. Then, when the code tries to access it in lines 102/104 and 106/108 region is not an empty pointer anymore.

PR validation:

I verified that the undefined behavior error disappears by running the workflow 11650.0 in CMSSW_12_1_UBSAN_X_2021-09-13-1100 release.

The code have a clean build without errors and pass the basic tests (runTheMatrix.py -l limited -i all --ibeos) when running with CMSSW_12_1_X_2021-09-23-2300. I have also checked out the dependencies and the code format.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-35452/25609

• This PR adds an extra 20KB to repository

• There are other open Pull requests which might conflict with changes you have proposed:

  • File RecoMuon/TrackerSeedGenerator/plugins/TSGFromL2Muon.cc modified in PR(s): Migrate TrackingRegions to esConsumes #35393
  • File RecoTracker/TkTrackingRegions/interface/RectangularEtaPhiTrackingRegion.h modified in PR(s): Migrate TrackingRegions to esConsumes #35393
  • File RecoTracker/TkTrackingRegions/interface/TrackingRegion.h modified in PR(s): Migrate TrackingRegions to esConsumes #35393

[cmsbuild]

A new Pull Request was created by @CeliaFernandez (Celia Fernández Madrazo) for master.

It involves the following packages:

• RecoMuon/TrackerSeedGenerator (reconstruction)
• RecoTracker/TkTrackingRegions (reconstruction)

@jpata, @cmsbuild, @slava77 can you please review it and eventually sign? Thanks.
@sscruz, @jhgoh, @trocino, @calderona, @felicepantaleo, @abbiendi, @GiacomoSguazzoni, @JanFSchulte, @rovere, @VinInn, @bellan, @HuguesBrun, @ebrondol, @Fedespring, @gpetruc, @mmusich, @mtosi, @dgulhan, @cericeci, @rociovilar this is something you requested to watch as well.
@perrotta, @dpiparo, @qliphy you are the release manager for this.

cms-bot commands are listed here

[slava77]

@cmsbuild please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4d0d74/19206/summary.html
COMMIT: 157c420
CMSSW: CMSSW_12_1_X_2021-09-28-1100/slc7_amd64_gcc900
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/35452/19206/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 4 differences found in the comparisons
• DQMHistoTests: Total files compared: 40
• DQMHistoTests: Total histograms compared: 3211080
• DQMHistoTests: Total failures: 5
• DQMHistoTests: Total nulls: 1
• DQMHistoTests: Total successes: 3211052
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: -0.004 KiB( 39 files compared)
• DQMHistoSizes: changed ( 312.0 ): -0.004 KiB MessageLogger/Warnings
• Checked 169 log files, 37 edm output root files, 40 DQM output files
• TriggerResults: no differences found

[slava77]

+reconstruction

for #35452 157c420

• code changes are somewhat technical in line with the PR description
  • it looks like the reference to nullptr here is never actually used (otherwise we'd see crashes). The case reported by UBSAN seems related to the line theTkSeedGenerator->trackerSeeds(staCand, *region, tTopo, tkSeeds); where the actual function call TSGFromL2Muon::trackerSeeds execution does not depend on *region.
• jenkins tests pass and comparisons with the baseline show no (relevant) differences

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)

[perrotta]

+1