Revert "dm: Remove root permission check in bd_dm_map_exists"

[vojtechtrefny]

This reverts commit 80ba38c.

Unfortunately blivet depends on libblockdev returning this specific error message.

Summary by CodeRabbit

• Bug Fixes
  • Implemented access control enforcement for Device Mapper functionality. The system now validates that users possess root or administrator privileges before permitting Device Mapper operations. All Device Mapper-related tasks and queries will be restricted from non-privileged users, with appropriate error messaging provided. This change improves security and prevents unauthorized access.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a root user permission check to the bd_dm_map_exists function in the device-mapper plugin. If the effective user ID is not 0 (root), the function sets the BD_DM_ERROR_NOT_ROOT error and returns FALSE immediately before any DM operations proceed.

Changes

Cohort / File(s)	Summary
Root user permission check src/plugins/dm.c	Added precondition in bd_dm_map_exists to verify effective user ID is 0 (root). Returns early with BD_DM_ERROR_NOT_ROOT error if not running as root, preventing subsequent DM task operations.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: reverting a previous commit that removed a root permission check.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

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[tbzatek]

Fine with me 🐸