Linux Kernel up to 6.12.4 tailcall_freplace.c entry_freplace infinite loop

Summaryinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.12.4. This affects the function entry_freplace of the file tailcall_freplace.c. Performing a manipulation results in infinite loop. This vulnerability is known as CVE-2024-47794. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.12.4. It has been classified as critical. This affects the function entry_freplace of the file tailcall_freplace.c. The manipulation with an unknown input leads to a infinite loop vulnerability. CWE is classifying the issue as CWE-835. The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: bpf: Prevent tailcall infinite loop caused by freplace There is a potential infinite loop issue that can occur when using a combination of tail calls and freplace. In an upcoming selftest, the attach target for entry_freplace of tailcall_freplace.c is subprog_tc of tc_bpf2bpf.c, while the tail call in entry_freplace leads to entry_tc. This results in an infinite loop: entry_tc -> subprog_tc -> entry_freplace --tailcall-> entry_tc. The problem arises because the tail_call_cnt in entry_freplace resets to zero each time entry_freplace is executed, causing the tail call mechanism to never terminate, eventually leading to a kernel panic. To fix this issue, the solution is twofold: 1. Prevent updating a program extended by an freplace program to a prog_array map. 2. Prevent extending a program that is already part of a prog_array map with an freplace program. This ensures that: * If a program or its subprogram has been extended by an freplace program, it can no longer be updated to a prog_array map. * If a program has been added to a prog_array map, neither it nor its subprograms can be extended by an freplace program. Moreover, an extension program should not be tailcalled. As such, return -EINVAL if the program has a type of BPF_PROG_TYPE_EXT when adding it to a prog_array map. Additionally, fix a minor code style issue by replacing eight spaces with a tab for proper formatting.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2024-47794 since 01/09/2025. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 233479 (Ubuntu 24.10 : Linux kernel (Low Latency) vulnerabilities (USN-7380-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.12.5 eliminates this vulnerability. Applying the patch 987aa730bad3e1ef66d9f30182294daa78f6387d/d6083f040d5d8f8d748462c77e90547097df936e 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 databases at Tenable (233479) and CERT Bund (WID-SEC-2025-1439). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• SUSE Linux
• Dell Secure Connect Gateway

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Be aware that VulDB is the high quality source for vulnerability data.

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