CVE-2024-50223 in Linux
Summary
by MITRE • 11/09/2024
In the Linux kernel, the following vulnerability has been resolved:
sched/numa: Fix the potential null pointer dereference in task_numa_work()
When running stress-ng-vm-segv test, we found a null pointer dereference error in task_numa_work(). Here is the backtrace:
[323676.066985] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
...... [323676.067108] CPU: 35 PID: 2694524 Comm: stress-ng-vm-se
...... [323676.067113] pstate: 23401009 (nzCv daif +PAN -UAO +TCO +DIT +SSBS BTYPE=--)
[323676.067115] pc : vma_migratable+0x1c/0xd0
[323676.067122] lr : task_numa_work+0x1ec/0x4e0
[323676.067127] sp : ffff8000ada73d20
[323676.067128] x29: ffff8000ada73d20 x28: 0000000000000000 x27: 000000003e89f010
[323676.067130] x26: 0000000000080000 x25: ffff800081b5c0d8 x24: ffff800081b27000
[323676.067133] x23: 0000000000010000 x22: 0000000104d18cc0 x21: ffff0009f7158000
[323676.067135] x20: 0000000000000000 x19: 0000000000000000 x18: ffff8000ada73db8
[323676.067138] x17: 0001400000000000 x16: ffff800080df40b0 x15: 0000000000000035
[323676.067140] x14: ffff8000ada73cc8 x13: 1fffe0017cc72001 x12: ffff8000ada73cc8
[323676.067142] x11: ffff80008001160c x10: ffff000be639000c x9 : ffff8000800f4ba4
[323676.067145] x8 : ffff000810375000 x7 : ffff8000ada73974 x6 : 0000000000000001
[323676.067147] x5 : 0068000b33e26707 x4 : 0000000000000001 x3 : ffff0009f7158000
[323676.067149] x2 : 0000000000000041 x1 : 0000000000004400 x0 : 0000000000000000
[323676.067152] Call trace:
[323676.067153] vma_migratable+0x1c/0xd0
[323676.067155] task_numa_work+0x1ec/0x4e0
[323676.067157] task_work_run+0x78/0xd8
[323676.067161] do_notify_resume+0x1ec/0x290
[323676.067163] el0_svc+0x150/0x160
[323676.067167] el0t_64_sync_handler+0xf8/0x128
[323676.067170] el0t_64_sync+0x17c/0x180
[323676.067173] Code: d2888001 910003fd f9000bf3 aa0003f3 (f9401000)
[323676.067177] SMP: stopping secondary CPUs
[323676.070184] Starting crashdump kernel...
stress-ng-vm-segv in stress-ng is used to stress test the SIGSEGV error handling function of the system, which tries to cause a SIGSEGV error on return from unmapping the whole address space of the child process.
Normally this program will not cause kernel crashes. But before the munmap system call returns to user mode, a potential task_numa_work() for numa balancing could be added and executed. In this scenario, since the child process has no vma after munmap, the vma_next() in task_numa_work() will return a null pointer even if the vma iterator restarts from 0.
Recheck the vma pointer before dereferencing it in task_numa_work().
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Analysis
by VulDB Data Team • 10/02/2025
The vulnerability identified as CVE-2024-50223 represents a critical null pointer dereference in the Linux kernel's NUMA (Non-Uniform Memory Access) scheduling subsystem, specifically within the task_numa_work() function. This flaw occurs during the execution of stress-ng-vm-segv, a stress testing tool designed to evaluate system error handling capabilities by deliberately triggering SIGSEGV signals. The vulnerability manifests when a child process undergoes memory unmapping through the munmap system call, creating a race condition where NUMA balancing work can be scheduled and executed before the process's virtual memory areas (VMAs) are fully cleaned up. The kernel's task_numa_work() function, which manages NUMA-aware memory placement decisions, attempts to traverse the virtual memory area list using vma_next() function. However, when the process has been unmapped and no valid VMAs remain, vma_next() returns a null pointer that is subsequently dereferenced without proper validation, leading to a kernel panic and system crash.
The technical implementation of this vulnerability stems from inadequate null pointer validation within the NUMA balancing code path. The task_numa_work() function performs memory management operations related to NUMA placement decisions without first verifying that the virtual memory area pointer remains valid. This pattern violates fundamental kernel safety principles and represents a classic null pointer dereference vulnerability, which is categorized under CWE-476 as "NULL Pointer Dereference." The specific execution context involves the interaction between memory management subsystems and NUMA balancing mechanisms, where the timing of asynchronous task work execution creates an opportunity for accessing freed memory structures. The backtrace shows the execution flow starting from vma_migratable() function, which calls task_numa_work() with an invalid memory pointer, ultimately causing the kernel to attempt to access memory at virtual address 0x20, resulting in an unhandled NULL pointer dereference that triggers a kernel panic.
The operational impact of this vulnerability extends beyond simple system crashes, as it can be exploited to cause denial of service attacks against Linux systems running NUMA-aware workloads. Attackers could potentially craft malicious workloads that trigger the race condition repeatedly, leading to system instability and service disruption. The vulnerability affects systems where NUMA balancing is enabled and where memory-intensive applications or stress testing tools are executed, particularly in high-performance computing environments, cloud infrastructure, and server deployments. The issue is particularly concerning because it can be triggered through legitimate stress testing scenarios, making it difficult to distinguish from actual system failures. According to ATT&CK framework, this vulnerability maps to T1499.004 (Resource Hijacking) and T1566.002 (Phishing via Social Engineering) as it can be leveraged to disrupt system availability and potentially be used in more sophisticated attacks that exploit system instability to gain further access.
Mitigation strategies for CVE-2024-50223 should focus on immediate kernel updates that incorporate the fix for the null pointer dereference in task_numa_work(). The patch implements proper validation of virtual memory area pointers before dereferencing them, ensuring that the function checks for NULL values before proceeding with memory access operations. System administrators should prioritize updating their kernel versions to patched releases and monitor for any system instability or unexpected crashes that might indicate the vulnerability is still present. Additional defensive measures include implementing proper NUMA balancing configuration, disabling NUMA balancing for applications that are known to trigger this condition, and monitoring system logs for kernel panic messages related to memory management. Organizations should also consider implementing intrusion detection systems that can identify unusual patterns of system calls related to memory management and NUMA operations, as these could indicate exploitation attempts. The fix aligns with security best practices for kernel development, emphasizing the importance of defensive programming techniques and proper resource validation in kernel space code execution.