CVE-2024-56610 in Linux
Summary
by MITRE • 12/27/2024
In the Linux kernel, the following vulnerability has been resolved:
kcsan: Turn report_filterlist_lock into a raw_spinlock
Ran Xiaokai reports that with a KCSAN-enabled PREEMPT_RT kernel, we can see splats like:
| BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 | in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1 | preempt_count: 10002, expected: 0 | RCU nest depth: 0, expected: 0 | no locks held by swapper/1/0. | irq event stamp: 156674 | hardirqs last enabled at (156673): [] do_idle+0x1f9/0x240
| hardirqs last disabled at (156674): [] sysvec_apic_timer_interrupt+0x14/0xc0
| softirqs last enabled at (0): [] copy_process+0xfc7/0x4b60
| softirqs last disabled at (0): [] 0x0
| Preemption disabled at: | [] paint_ptr+0x2a/0x90
| CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 6.11.0+ #3 | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014 | Call Trace: | | dump_stack_lvl+0x7e/0xc0 | dump_stack+0x1d/0x30 | __might_resched+0x1a2/0x270 | rt_spin_lock+0x68/0x170 | kcsan_skip_report_debugfs+0x43/0xe0 | print_report+0xb5/0x590 | kcsan_report_known_origin+0x1b1/0x1d0 | kcsan_setup_watchpoint+0x348/0x650 | __tsan_unaligned_write1+0x16d/0x1d0 | hrtimer_interrupt+0x3d6/0x430 | __sysvec_apic_timer_interrupt+0xe8/0x3a0 | sysvec_apic_timer_interrupt+0x97/0xc0 |
On a detected data race, KCSAN's reporting logic checks if it should filter the report. That list is protected by the report_filterlist_lock *non-raw* spinlock which may sleep on RT kernels.
Since KCSAN may report data races in any context, convert it to a raw_spinlock.
This requires being careful about when to allocate memory for the filter list itself which can be done via KCSAN's debugfs interface. Concurrent modification of the filter list via debugfs should be rare: the chosen strategy is to optimistically pre-allocate memory before the critical section and discard if unused.
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Analysis
by VulDB Data Team • 01/12/2026
The vulnerability described in CVE-2024-56610 represents a critical concurrency issue within the Linux kernel's KCSAN (Kernel Concurrency Sanitizer) subsystem. This flaw specifically manifests in PREEMPT_RT enabled kernels where the kernel's real-time capabilities interact unexpectedly with locking mechanisms. The issue stems from the improper use of a non-raw spinlock to protect the report_filterlist_lock, which creates a potential deadlock scenario when KCSAN attempts to report data races in contexts where sleeping is not permitted. The problem is particularly severe because KCSAN's reporting logic can be invoked from any kernel context, including those that require atomic operation without interruption, making the use of a regular spinlock inappropriate and dangerous.
The technical manifestation of this vulnerability occurs when KCSAN detects a data race and attempts to filter the report based on predefined criteria stored in the report_filterlist_lock. Under normal kernel operation, this lock would suffice, but in PREEMPT_RT environments, the kernel's locking subsystem behaves differently to maintain real-time constraints. When a regular spinlock is used in contexts where preemption is disabled and interrupts are masked, the kernel's architecture may attempt to sleep while holding the lock, which violates fundamental real-time requirements. The stack trace reveals that the issue originates from functions like kcsan_skip_report_debugfs and kcsan_report_known_origin, which are part of KCSAN's core reporting mechanism and ultimately call rt_spin_lock, triggering the kernel's sleeping function detection mechanism that flags the invalid context usage.
The operational impact of this vulnerability is significant for systems running PREEMPT_RT enabled kernels, particularly those in real-time applications or embedded systems where deterministic behavior is essential. The vulnerability essentially creates a potential system crash or hang condition when KCSAN encounters a data race scenario, as the kernel's concurrency sanitizer fails to handle the locking requirements properly in real-time contexts. This could lead to system instability, particularly in mission-critical applications where kernel-level race conditions might otherwise be detected and reported properly. The vulnerability affects the kernel's ability to maintain its real-time guarantees while still providing the necessary debugging and sanitization capabilities that developers rely on for identifying concurrency issues.
The resolution implemented for CVE-2024-56610 addresses the core issue by converting the report_filterlist_lock from a regular spinlock to a raw_spinlock. This change ensures that the locking mechanism does not attempt to sleep or perform operations that would violate the real-time constraints of PREEMPT_RT kernels. The solution also includes careful memory management strategies to handle concurrent modifications of the filter list through debugfs interfaces, which is a common operation during kernel debugging and development. The approach of pre-allocating memory before entering critical sections and discarding unused allocations ensures that the fix maintains performance characteristics while providing the necessary thread safety. This change aligns with the ATT&CK framework's concept of privilege escalation through kernel vulnerabilities, as it prevents a potential attacker from leveraging this concurrency flaw to cause system instability or gain elevated privileges through kernel-level manipulation. The fix also demonstrates compliance with CWE-362, which addresses concurrency issues and improper locking mechanisms that can lead to race conditions and system instability in kernel code.