Linux Kernel up to 6.10.6 libfs simple_dir_operations infinite loop

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.10.6. It has been declared as problematic. Affected by this issue is the function simple_dir_operations of the component libfs. Such manipulation leads to an unknown weakness. This vulnerability is listed as CVE-2024-46701. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.10.6. It has been rated as problematic. Affected by this issue is the function simple_dir_operations of the component libfs. Using CWE to declare the problem leads to CWE-835. The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: libfs: fix infinite directory reads for offset dir After we switch tmpfs dir operations from simple_dir_operations to simple_offset_dir_operations, every rename happened will fill new dentry to dest dir's maple tree(&SHMEM_I(inode)->dir_offsets->mt) with a free key starting with octx->newx_offset, and then set newx_offset equals to free key + 1. This will lead to infinite readdir combine with rename happened at the same time, which fail generic/736 in xfstests(detail show as below). 1. create 5000 files(1 2 3...) under one dir 2. call readdir(man 3 readdir) once, and get one entry 3. rename(entry, "TEMPFILE"), then rename("TEMPFILE", entry) 4. loop 2~3, until readdir return nothing or we loop too many times(tmpfs break test with the second condition) We choose the same logic what commit 9b378f6ad48cf ("btrfs: fix infinite directory reads") to fix it, record the last_index when we open dir, and do not emit the entry which index >= last_index. The file->private_data now used in offset dir can use directly to do this, and we also update the last_index when we llseek the dir file. [brauner: only update last_index after seek when offset is zero like Jan suggested]

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2024-46701 since 09/11/2024. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 212724 (Ubuntu 22.04 LTS / 24.04 LTS : Linux kernel vulnerabilities (USN-7154-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.10.7 eliminates this vulnerability. Applying the patch 308b4fc2403b/64a7ce76fb90 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (212724). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.10.0
• 6.10.1
• 6.10.2
• 6.10.3
• 6.10.4
• 6.10.5
• 6.10.6

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion