CVE-2024-41023: sched/deadline: Fix task_struct reference leak

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-07-29 · updated 2026-10-30
Weakness: CWE-401

Description

In the Linux kernel, the following vulnerability has been resolved: sched/deadline: Fix task_struct reference leak During the execution of the following stress test with linux-rt: stress-ng --cyclic 30 --timeout 30 --minimize --quiet kmemleak frequently reported a memory leak concerning the task_struct: unreferenced object 0xffff8881305b8000 (size 16136): comm "stress-ng", pid 614, jiffies 4294883961 (age 286.412s) object hex dump (first 32 bytes): 02 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 .@.............. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ debug hex dump (first 16 bytes): 53 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 S............... backtrace: [<00000000046b6790>] dup_task_struct+0x30/0x540 [<00000000c5ca0f0b>] copy_process+0x3d9/0x50e0 [<00000000ced59777>] kernel_clone+0xb0/0x770 [<00000000a50befdc>] __do_sys_clone+0xb6/0xf0 [<000000001dbf2008>] do_syscall_64+0x5d/0xf0 [<00000000552900ff>] entry_SYSCALL_64_after_hwframe+0x6e/0x76 The issue occurs in start_dl_timer(), which increments the task_struct reference count and sets a timer. The timer callback, dl_task_timer, is supposed to decrement the reference count upon expiration. However, if enqueue_task_dl() is called before the timer expires and cancels it, the reference count is not decremented, leading to the leak. This patch fixes the reference leak by ensuring the task_struct reference count is properly decremented when the timer is canceled.

Affected products

Linux kernel: from 4.19.257 before 4.20; from 5.4.212 before 5.5; from 5.10 before 6.9.10; 6.10-rc1, 6.10-rc2, 6.10-rc3, 6.10-rc4, 6.10-rc5, 6.10-rc6 (+1) — fixed in 4.20, 5.5, 6.9.10
Linux: from 4.19.257 before 4.20; from 5.4.212 before 5.5 — fixed in 4.20, 5.5

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.5, 6.9.10; Linux 4.20, 5.5. Check the vendor advisory for mitigations.

References

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