CVE: CVE-2024-42103

Descrizione: This log snippet describes a potential bug in the `btrfs_delete_unused_bgs()` function, which is responsible for handling unused btrfs blocks. Let’s break down the issue and its implications: **The Problem: Incorrect Use of the Unused List** The core of the bug lies in how the `btrfs_delete_unused_bgs()` function handles the unused btrfs block list. The log indicates that the function *incorrectly* treats the unused list as a “safe” area. It’s designed to ensure that unused blocks are *never* added to the reclaim list, preventing potential issues with reclaim operations. **The Explanation** 1. **`space_info->groups_sem in write mode`:** The log mentions that the code is in write mode, meaning it’s modifying the block group’s metadata. This is crucial. 2. **The Logic:** The function checks if the `space_info->groups_sem` values (which represent the block group’s metadata) are still 0 under the block group’s lock. This is the key. The log suggests that this check *should* be sufficient to prevent the unused block list from being added to the reclaim list. 3. **The Bug:** The bug occurs when the `space_info->groups_sem` values are *not* 0. This means the function is incorrectly assuming that the unused block list is safe. It’s not properly accounting for the potential for other tasks to *potentially* allocate space from the block group. **Why is this a problem?** * **Reclaim List Issues:** The reclaim list is a critical area for btrfs to manage. If the function incorrectly treats the unused list as safe, it could lead to problems when btrfs tries to reclaim unused blocks. * **ENOSPC Error:** The log mentions “ENOSPC” (Error Not Set to Present), which is a potential error condition. This suggests that the reclaim list is being incorrectly set, potentially leading to data corruption or instability. **In simpler terms:** The code is incorrectly assuming that the unused block list is safe, which could cause problems when btrfs tries to reclaim unused blocks. **What’s being done to fix it?** The log snippet indicates that the bug was fixed by a retry_list code. This code is designed to ensure that the used bytes of a block group are 0 when it’s added to the unused list. This is a crucial step in preventing the bug. **Key Takeaway:** This log highlights a critical design flaw in the `btrfs_delete_unused_bgs()` function. It’s essential to understand that the function’s logic regarding the unused list needs to be carefully validated to prevent potential problems with reclaim operations. The fix involves ensuring that the unused list is properly marked as safe.

Vettore di attacco

Riferimenti esterni

• https://git.kernel.org/stable/c/522b39bd7163e8dc49f8cf10b9b782218ac48746
• https://git.kernel.org/stable/c/aa1d8cc0cc500e06b316cd6732d4e6c1388fe33c
• https://git.kernel.org/stable/c/f8e960be923f74a273c62478c9cab9523936752b
• https://git.kernel.org/stable/c/326fa14549d7969ef80d3f5beea5470cd1c8e67f
• https://git.kernel.org/stable/c/48f091fd50b2eb33ae5eaea9ed3c4f81603acf38

Prodotti interessati

• Linux – Linux
• Linux – Linux

Relazioni con altri prodotti

Produttore:Linux
Prodotto: Linux
Anno: 2024
CWE:
CVSS: 0.0

Ulteriori risorse disponibili

• Vulnerabilità scoperte nello stesso anno (2024)