CVE-2024-26724 in Linux
Summary
by MITRE • 04/03/2024
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: DPLL, Fix possible use after free after delayed work timer triggers
I managed to hit following use after free warning recently:
[ 2169.711665] ==================================================================
[ 2169.714009] BUG: KASAN: slab-use-after-free in __run_timers.part.0+0x179/0x4c0
[ 2169.716293] Write of size 8 at addr ffff88812b326a70 by task swapper/4/0
[ 2169.719022] CPU: 4 PID: 0 Comm: swapper/4 Not tainted 6.8.0-rc2jiri+ #2
[ 2169.720974] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[ 2169.722457] Call Trace:
[ 2169.722756]
[ 2169.723024] dump_stack_lvl+0x58/0xb0
[ 2169.723417] print_report+0xc5/0x630
[ 2169.723807] ? __virt_addr_valid+0x126/0x2b0
[ 2169.724268] kasan_report+0xbe/0xf0
[ 2169.724667] ? __run_timers.part.0+0x179/0x4c0
[ 2169.725116] ? __run_timers.part.0+0x179/0x4c0
[ 2169.725570] __run_timers.part.0+0x179/0x4c0
[ 2169.726003] ? call_timer_fn+0x320/0x320
[ 2169.726404] ? lock_downgrade+0x3a0/0x3a0
[ 2169.726820] ? kvm_clock_get_cycles+0x14/0x20
[ 2169.727257] ? ktime_get+0x92/0x150
[ 2169.727630] ? lapic_next_deadline+0x35/0x60
[ 2169.728069] run_timer_softirq+0x40/0x80
[ 2169.728475] __do_softirq+0x1a1/0x509
[ 2169.728866] irq_exit_rcu+0x95/0xc0
[ 2169.729241] sysvec_apic_timer_interrupt+0x6b/0x80
[ 2169.729718]
[ 2169.729993]
[ 2169.730259] asm_sysvec_apic_timer_interrupt+0x16/0x20
[ 2169.730755] RIP: 0010:default_idle+0x13/0x20
[ 2169.731190] Code: c0 08 00 00 00 4d 29 c8 4c 01 c7 4c 29 c2 e9 72 ff ff ff cc cc cc cc 8b 05 9a 7f 1f 02 85 c0 7e 07 0f 00 2d cf 69 43 00 fb f4 c3 66 66 2e 0f 1f 84 00 00 00 00 00 65 48 8b 04 25 c0 93 04 00
[ 2169.732759] RSP: 0018:ffff888100dbfe10 EFLAGS: 00000242
[ 2169.733264] RAX: 0000000000000001 RBX: ffff888100d9c200 RCX: ffffffff8241bd62
[ 2169.733925] RDX: ffffed109a848b15 RSI: 0000000000000004 RDI: ffffffff8127ac55
[ 2169.734566] RBP: 0000000000000004 R08: 0000000000000000 R09: ffffed109a848b14
[ 2169.735200] R10: ffff8884d42458a3 R11: 000000000000ba7e R12: ffffffff83d7d3a0
[ 2169.735835] R13: 1ffff110201b7fc6 R14: 0000000000000000 R15: ffff888100d9c200
[ 2169.736478] ? ct_kernel_exit.constprop.0+0xa2/0xc0
[ 2169.736954] ? do_idle+0x285/0x290
[ 2169.737323] default_idle_call+0x63/0x90
[ 2169.737730] do_idle+0x285/0x290
[ 2169.738089] ? arch_cpu_idle_exit+0x30/0x30
[ 2169.738511] ? mark_held_locks+0x1a/0x80
[ 2169.738917] ? lockdep_hardirqs_on_prepare+0x12e/0x200
[ 2169.739417] cpu_startup_entry+0x30/0x40
[ 2169.739825] start_secondary+0x19a/0x1c0
[ 2169.740229] ? set_cpu_sibling_map+0xbd0/0xbd0
[ 2169.740673] secondary_startup_64_no_verify+0x15d/0x16b
[ 2169.741179]
[ 2169.741686] Allocated by task 1098:
[ 2169.742058] kasan_save_stack+0x1c/0x40
[ 2169.742456] kasan_save_track+0x10/0x30
[ 2169.742852] __kasan_kmalloc+0x83/0x90
[ 2169.743246] mlx5_dpll_probe+0xf5/0x3c0 [mlx5_dpll]
[ 2169.743730] auxiliary_bus_probe+0x62/0xb0
[ 2169.744148] really_probe+0x127/0x590
[ 2169.744534] __driver_probe_device+0xd2/0x200
[ 2169.744973] device_driver_attach+0x6b/0xf0
[ 2169.745402] bind_store+0x90/0xe0
[ 2169.745761] kernfs_fop_write_iter+0x1df/0x2a0
[ 2169.746210] vfs_write+0x41f/0x790
[ 2169.746579] ksys_write+0xc7/0x160
[ 2169.746947] do_syscall_64+0x6f/0x140
[ 2169.747333] entry_SYSCALL_64_after_hwframe+0x46/0x4e
[ 2169.748049] Freed by task 1220:
[ 2169.748393] kasan_save_stack+0x1c/0x40
[ 2169.748789] kasan_save_track+0x10/0x30
[ 2169.749188] kasan_save_free_info+0x3b/0x50
[ 2169.749621] poison_slab_object+0x106/0x180
[ 2169.750044] __kasan_slab_free+0x14/0x50
[ 2169.750451] kfree+0x118/0x330
[ 2169.750792] mlx5_dpll_remove+0xf5/0x110 [mlx5_dpll]
[ 2169.751271] auxiliary_bus_remove+0x2e/0x40
[ 2169.751694] device_release_driver_internal+0x24b/0x2e0
[ 2169.752191] unbind_store+0xa6/0xb0
[ 2169.752563] kernfs_fo
---truncated---
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Analysis
by VulDB Data Team • 08/03/2025
The vulnerability described in CVE-2024-26724 resides within the Linux kernel's mlx5_dpll driver, specifically concerning the handling of delayed work timers. This issue manifests as a use-after-free condition that occurs when a timer callback executes after the associated data structure has already been freed. The root cause lies in improper synchronization and lifecycle management of kernel objects tied to the DPLL (Digital Phase Locked Loop) functionality, which is used for precise time synchronization in Mellanox network adapters. When the mlx5_dpll_remove function is invoked during driver removal, it frees memory associated with the DPLL structure, but a timer callback scheduled via delayed work may still execute afterward, attempting to access the already-freed memory region. This type of vulnerability is classified under CWE-416 as use-after-free, where memory is accessed after it has been freed, potentially leading to undefined behavior, system crashes, or privilege escalation.
The technical flaw arises from the interaction between the kernel's timer subsystem and the mlx5_dpll driver's cleanup mechanism. During normal operation, the driver allocates memory for DPLL structures and schedules timer callbacks to manage asynchronous operations. However, when the driver is unloaded, the mlx5_dpll_remove function frees these structures, yet timer callbacks that were scheduled but not yet executed can still trigger, resulting in access to freed memory. The kernel's KASAN (Kernel Address Sanitizer) detection confirms this condition by reporting a write operation of size 8 to address 0xffff88812b326a70, which had been freed by task 1220, while being accessed by task swapper/4/0 during timer execution. This behavior violates fundamental memory safety principles and can be exploited to cause system instability or potentially enable privilege escalation depending on the context in which the freed memory is accessed.
The operational impact of this vulnerability is significant in environments where Mellanox network adapters with DPLL support are deployed, particularly in high-precision timing applications such as financial trading systems, telecommunications infrastructure, or real-time control systems. An attacker who can trigger the specific sequence of events leading to the use-after-free condition may cause system crashes, leading to denial of service, or potentially leverage the instability to execute arbitrary code with kernel privileges. The vulnerability is particularly concerning because it can be triggered during normal driver load/unload cycles, making it difficult to predict or prevent in production environments. The ATT&CK framework categorizes this under privilege escalation through kernel exploits, specifically targeting the kernel memory management subsystem and potentially enabling lateral movement within a compromised system.
Mitigation strategies for this vulnerability include applying the kernel patch that resolves the synchronization issue between timer callbacks and resource deallocation in the mlx5_dpll driver. The fix typically involves ensuring proper locking mechanisms or reference counting to prevent timer callbacks from executing after the associated data structures have been freed. System administrators should prioritize updating to kernel versions that contain the patched code, particularly those incorporating the fix for CVE-2024-26724. Additionally, monitoring for KASAN reports and system stability issues related to mlx5_dpll driver operations can help identify potential exploitation attempts. Organizations using Mellanox network hardware should also consider implementing runtime protections such as kernel lockdown modes or memory protection features to reduce the attack surface. Regular security audits of kernel modules and driver interactions are recommended to identify similar race conditions that could lead to similar vulnerabilities in other subsystems.