CVE-2024-50079 in Linux
Summary
by MITRE • 10/29/2024
In the Linux kernel, the following vulnerability has been resolved:
io_uring/sqpoll: ensure task state is TASK_RUNNING when running task_work
When the sqpoll is exiting and cancels pending work items, it may need to run task_work. If this happens from within io_uring_cancel_generic(), then it may be under waiting for the io_uring_task waitqueue. This results in the below splat from the scheduler, as the ring mutex may be attempted grabbed while in a TASK_INTERRUPTIBLE state.
Ensure that the task state is set appropriately for that, just like what is done for the other cases in io_run_task_work().
do not call blocking ops when !TASK_RUNNING; state=1 set at [] prepare_to_wait+0x88/0x2fc
WARNING: CPU: 6 PID: 59939 at kernel/sched/core.c:8561 __might_sleep+0xf4/0x140 Modules linked in: CPU: 6 UID: 0 PID: 59939 Comm: iou-sqp-59938 Not tainted 6.12.0-rc3-00113-g8d020023b155 #7456 Hardware name: linux,dummy-virt (DT) pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) pc : __might_sleep+0xf4/0x140 lr : __might_sleep+0xf4/0x140 sp : ffff80008c5e7830 x29: ffff80008c5e7830 x28: ffff0000d93088c0 x27: ffff60001c2d7230 x26: dfff800000000000 x25: ffff0000e16b9180 x24: ffff80008c5e7a50 x23: 1ffff000118bcf4a x22: ffff0000e16b9180 x21: ffff0000e16b9180 x20: 000000000000011b x19: ffff80008310fac0 x18: 1ffff000118bcd90 x17: 30303c5b20746120 x16: 74657320313d6574 x15: 0720072007200720 x14: 0720072007200720 x13: 0720072007200720 x12: ffff600036c64f0b x11: 1fffe00036c64f0a x10: ffff600036c64f0a x9 : dfff800000000000 x8 : 00009fffc939b0f6 x7 : ffff0001b6327853 x6 : 0000000000000001 x5 : ffff0001b6327850 x4 : ffff600036c64f0b x3 : ffff8000803c35bc x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000e16b9180 Call trace: __might_sleep+0xf4/0x140 mutex_lock+0x84/0x124 io_handle_tw_list+0xf4/0x260 tctx_task_work_run+0x94/0x340 io_run_task_work+0x1ec/0x3c0 io_uring_cancel_generic+0x364/0x524 io_sq_thread+0x820/0x124c ret_from_fork+0x10/0x20
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Analysis
by VulDB Data Team • 10/02/2025
The vulnerability identified as CVE-2024-50079 resides within the Linux kernel's io_uring subsystem, specifically concerning the sqpoll (single queue poll) mechanism. This flaw manifests when the sqpoll thread is in the process of exiting and attempting to cancel pending work items, which necessitates running task_work. The issue arises from an improper handling of task states during this operation, leading to potential scheduler deadlocks and system instability. The vulnerability occurs in the context of io_uring_cancel_generic(), a function responsible for canceling operations within the io_uring framework, where it may be executing under a waitqueue condition that prevents proper task state management. When task_work is invoked from this context, the kernel scheduler detects an attempt to acquire a mutex while the task is in TASK_INTERRUPTIBLE state, which violates kernel locking rules and triggers the __might_sleep warning.
The technical root cause of this vulnerability stems from the failure to properly set the task state to TASK_RUNNING before executing blocking operations within the io_run_task_work() function. According to CWE-691, this represents an insufficient control flow management issue where blocking operations are performed in inappropriate task states. The kernel's scheduler enforces strict rules about when blocking operations can occur, and attempting to acquire locks while a task is in TASK_INTERRUPTIBLE state violates these principles. The error message indicates that the system attempted to grab a mutex while in a state that does not allow sleeping, which is a fundamental violation of kernel design principles. The stack trace shows the sequence leading to the failure: io_uring_cancel_generic calls io_run_task_work, which then calls tctx_task_work_run, followed by io_handle_tw_list, and finally mutex_lock, which triggers the __might_sleep warning. This behavior directly conflicts with the kernel's locking subsystem requirements as defined in the Linux kernel documentation.
The operational impact of this vulnerability is significant as it can lead to system hangs, deadlocks, and potential denial of service conditions within systems heavily reliant on io_uring for high-performance I/O operations. Systems using io_uring with sqpoll threads, particularly those handling high volumes of asynchronous I/O requests, are at risk of experiencing unresponsive behavior when the cancellation logic is triggered during thread shutdown. The vulnerability affects the kernel's ability to maintain consistent state management during task work execution, potentially causing cascading failures in applications that depend on io_uring for efficient I/O processing. This issue is particularly concerning in server environments where I/O performance and reliability are critical, as it could lead to complete system unresponsiveness under certain load conditions. The ATT&CK framework categorizes this under privilege escalation and system stability manipulation, as the vulnerability can be exploited to cause system instability and potentially gain unauthorized access to system resources through denial of service attacks.
Mitigation strategies for this vulnerability involve ensuring that task states are properly managed before executing blocking operations within the io_uring subsystem. The fix implemented in the kernel ensures that task state is correctly set to TASK_RUNNING when running task_work, aligning with established patterns used elsewhere in the io_run_task_work() function. This approach prevents the scheduler from entering a state where mutex acquisition is attempted while the task is in an inappropriate state for sleeping operations. System administrators should ensure that all systems running affected kernel versions are updated to the patched version that addresses this specific task state management issue. The patch essentially enforces proper state transitions before task_work execution, preventing the race condition that leads to the scheduler warning. Additionally, monitoring systems for kernel warnings related to __might_sleep and mutex operations can help identify potential exploitation attempts or system instability before they escalate into complete service disruptions. Organizations should prioritize kernel updates and maintain robust testing procedures for io_uring-based applications to prevent this vulnerability from being exploited in production environments.