Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix cleanup race condition with exclusive and shared lock files #5319

Open
wants to merge 2 commits into
base: master
Choose a base branch
from

Conversation

ma30002000
Copy link
Contributor

@ma30002000 ma30002000 commented Oct 14, 2024

Description

Since on unix file opening and locking are non-atomic operations (open() system call followed with a flock() call), and clean.py depends on exclusive lockability to in order to decide on zombie file deletion, the following race condition (although rare) exists:

RobustExclusiveLock.hpp RobustExclusiveLock::open_and_lock_file calls open() successfully
clean.py opens, successfully locks and deletes the file
RobustExclusiveLock.hpp RobustExclusiveLock::open_and_lock_file calls flock() successfully

This leads to the file's creator assuming a successful file creation (the fd is valid and usable), while in reality the file is not accessible anymore since its directory entry has been removed. A similar situation might be triggered in obustSharedLock.hpp.

Verifying the existence of the directory entry with a call to stat() after successfully obtaining the exclusive lock of the file fixes and restarting the open and lock procedure in case the file was removed in between seems to fix the behavior.

@Mergifyio backport 3.1.x 3.0.x 2.14.x 2.10.x

Contributor Checklist

  • Commit messages follow the project guidelines.
  • The code follows the style guidelines of this project.
  • N/A Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
  • N/A Any new/modified methods have been properly documented using Doxygen.
  • N/A Any new configuration API has an equivalent XML API (with the corresponding XSD extension)
  • Changes are backport compatible: they do NOT break ABI nor change library core behavior.
  • Changes are API compatible.
  • N/A New feature has been added to the versions.md file (if applicable).
  • N/A New feature has been documented/Current behavior is correctly described in the documentation.
  • Applicable backports have been included in the description.

Reviewer Checklist

  • The PR has a milestone assigned.
  • The title and description correctly express the PR's purpose.
  • Check contributor checklist is correct.
  • N/A If this is a critical bug fix, backports to the critical-only supported branches have been requested.
  • Check CI results: changes do not issue any warning.
  • Check CI results: failing tests are unrelated with the changes.

@ma30002000 ma30002000 force-pushed the bugfix/fix-open-lock-racecondition branch from 850df66 to 109deba Compare October 14, 2024 12:38
@JesusPoderoso JesusPoderoso added this to the v3.1.1 milestone Oct 14, 2024
@JesusPoderoso JesusPoderoso changed the title Fix cleanup race condition with exclusive and shareed lock files [21861] Fix cleanup race condition with exclusive and shared lock files Oct 14, 2024
@JesusPoderoso JesusPoderoso added the needs-review PR that is ready to be reviewed label Oct 14, 2024
@ma30002000
Copy link
Contributor Author

Note that this PR does NOT address #21861, which deals with files missing from the cleanup procedure.

@ma30002000 ma30002000 changed the title [21861] Fix cleanup race condition with exclusive and shared lock files Fix cleanup race condition with exclusive and shared lock files Oct 14, 2024
@ma30002000
Copy link
Contributor Author

ma30002000 commented Oct 14, 2024

I have removed the references to #5308 since this PR deals with a different issue.

@JesusPoderoso JesusPoderoso modified the milestones: v3.1.1, v3.2.0 Oct 17, 2024
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
needs-review PR that is ready to be reviewed
Projects
None yet
Development

Successfully merging this pull request may close these issues.

2 participants