CVE-2024-47703 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
bpf, lsm: Add check for BPF LSM return value
A bpf prog returning a positive number attached to file_alloc_security hook makes kernel panic.
This happens because file system can not filter out the positive number returned by the LSM prog using IS_ERR, and misinterprets this positive number as a file pointer.
Given that hook file_alloc_security never returned positive number before the introduction of BPF LSM, and other BPF LSM hooks may encounter similar issues, this patch adds LSM return value check in verifier, to ensure no unexpected value is returned.
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Analysis
by VulDB Data Team • 01/19/2026
The vulnerability described in CVE-2024-47703 represents a critical flaw in the Linux kernel's security module architecture that specifically affects the BPF (Berkeley Packet Filter) LSM (Linux Security Module) integration. This issue manifests when a BPF program attached to the file_alloc_security hook returns a positive numeric value, which subsequently triggers a kernel panic. The root cause lies in the improper handling of return values from LSM programs, particularly within the BPF framework where the kernel fails to validate the output of security modules before processing it as a valid file pointer reference. The vulnerability specifically targets the kernel's security subsystem and represents a failure in input validation that could be exploited to cause system-wide instability.
The technical implementation flaw occurs within the kernel's BPF verifier component which lacks proper validation of return values from LSM programs. When a BPF program attached to the file_alloc_security hook executes and returns a positive integer value, the kernel's security infrastructure does not employ the standard IS_ERR() macro checking mechanism that would normally prevent such values from being interpreted as valid file pointers. This oversight creates a scenario where legitimate security module return codes can be misinterpreted as memory addresses, leading to memory corruption and ultimately a kernel panic. The vulnerability is particularly concerning because the file_alloc_security hook was never designed to return positive values in the kernel's historical implementation, making this behavior a clear deviation from expected security module semantics. The issue extends beyond just this single hook as similar problems may exist across other BPF LSM integration points, indicating a systemic validation gap in the kernel's security module handling.
The operational impact of this vulnerability is severe and potentially catastrophic for systems running affected kernel versions. A malicious BPF program could be crafted to exploit this vulnerability by returning positive values from the file_alloc_security hook, thereby causing immediate system crashes and denial of service conditions. This vulnerability affects the fundamental security infrastructure of Linux systems, potentially compromising system availability and stability. The kernel panic resulting from this flaw would require system administrators to perform manual restarts, disrupting services and potentially leading to data loss if systems are not properly configured for automatic recovery. The vulnerability's exploitation does not require elevated privileges beyond those needed to load BPF programs, making it particularly dangerous in environments where BPF functionality is exposed to untrusted users or applications.
Mitigation strategies for CVE-2024-47703 focus on patching the kernel to implement proper return value validation within the BPF verifier component. The fix involves adding explicit checks for LSM return values during BPF program verification to ensure that programs cannot return unexpected positive values that would be misinterpreted as file pointers. System administrators should prioritize applying the kernel patches released by their respective distributions as soon as possible. Organizations should also implement monitoring for unauthorized BPF program loading and consider restricting BPF capabilities in environments where security is paramount. The fix aligns with the principle of least privilege and input validation, which are fundamental concepts in secure system design and correspond to CWE-248 (Uncaught Exception) and ATT&CK technique T1059.008 (Command and Scripting Interpreter: PowerShell). Additionally, system administrators should review existing BPF programs and security policies to ensure no programs are currently returning invalid values that could trigger this vulnerability, particularly focusing on LSM hook implementations that interact with file system operations.