Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: mm: slub: avoid wake up kswapd in set_track_prepare set_track_prepare() can… (CVE-2025-39843)
In the Linux kernel, the following vulnerability has been resolved: mm: slub: avoid wake up kswapd in set_track_prepare set_track_prepare() can incur lock recursion. The issue is that it is called from hrtimer_start_range_ns holding the per_cpu(hrtimer_bases)[n].lock, but when enabled CONFIG_DEBUG_OBJECTS_TIMERS, may wake up kswapd in set_track_prepare, and try to hold the per_cpu(hrtimer_bases)[n].lock. Avoid deadlock caused by implicitly waking up kswapd by passing in allocation flags, which do not contain __GFP_KSWAPD_RECLAIM in the debug_objects_fill_pool() case. Inside stack depot they are processed by gfp_nested_mask(). Since ___slab_alloc() has preemption disabled, we mask out __GFP_DIRECT_RECLAIM from the flags there. The oops looks something like: BUG: spinlock recursion on CPU#3, swapper/3/0 lock: 0xffffff8a4bf29c80, .magic: dead4ead, .owner: swapper/3/0, .owner_cpu: 3 Hardware name: Qualcomm Technologies, Inc. Popsicle based on SM8850 (DT) Call trace: spin_bug+0x0 _raw_spin_lock_irqsave+0x80 hrtimer_try_to_cancel+0x94 task_contending+0x10c enqueue_dl_entity+0x2a4 dl_server_start+0x74 enqueue_task_fair+0x568 enqueue_task+0xac do_activate_task+0x14c ttwu_do_activate+0xcc try_to_wake_up+0x6c8 default_wake_function+0x20 autoremove_wake_function+0x1c __wake_up+0xac wakeup_kswapd+0x19c wake_all_kswapds+0x78 __alloc_pages_slowpath+0x1ac __alloc_pages_noprof+0x298 stack_depot_save_flags+0x6b0 stack_depot_save+0x14 set_track_prepare+0x5c ___slab_alloc+0xccc __kmalloc_cache_noprof+0x470 __set_page_owner+0x2bc post_alloc_hook[jt]+0x1b8 prep_new_page+0x28 get_page_from_freelist+0x1edc __alloc_pages_noprof+0x13c alloc_slab_page+0x244 allocate_slab+0x7c ___slab_alloc+0x8e8 kmem_cache_alloc_noprof+0x450 debug_objects_fill_pool+0x22c debug_object_activate+0x40 enqueue_hrtimer[jt]+0xdc hrtimer_start_range_ns+0x5f8 ...
AI Analysis
Technical Summary
CVE-2025-39843 is a vulnerability in the Linux kernel's memory management (mm) subsystem, specifically in the slub allocator, where the wake up of the kswapd process in set_track_prepare is avoided to mitigate the issue. Red Hat has released a security update for Red Hat Enterprise Linux 9 to address this vulnerability. The advisory rates the impact as moderate and requires a system reboot after applying the update. No CVSS score is provided in the advisory. The vulnerability is tracked under CWE-833.
Potential Impact
The vulnerability affects the Linux kernel memory management subsystem and could potentially impact system stability or performance related to memory management. The exact impact details are not provided, but Red Hat rates this as a moderate security issue. There are no known exploits in the wild at this time.
Mitigation Recommendations
Red Hat has released an official security update for Red Hat Enterprise Linux 9 that addresses CVE-2025-39843. Users should apply the kernel update as described in the Red Hat advisory RHSA-2025:21926 and reboot their systems to ensure the fix takes effect. Patch status is confirmed as an official fix available from Red Hat.
Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: mm: slub: avoid wake up kswapd in set_track_prepare set_track_prepare() can… (CVE-2025-39843)
Description
In the Linux kernel, the following vulnerability has been resolved: mm: slub: avoid wake up kswapd in set_track_prepare set_track_prepare() can incur lock recursion. The issue is that it is called from hrtimer_start_range_ns holding the per_cpu(hrtimer_bases)[n].lock, but when enabled CONFIG_DEBUG_OBJECTS_TIMERS, may wake up kswapd in set_track_prepare, and try to hold the per_cpu(hrtimer_bases)[n].lock. Avoid deadlock caused by implicitly waking up kswapd by passing in allocation flags, which do not contain __GFP_KSWAPD_RECLAIM in the debug_objects_fill_pool() case. Inside stack depot they are processed by gfp_nested_mask(). Since ___slab_alloc() has preemption disabled, we mask out __GFP_DIRECT_RECLAIM from the flags there. The oops looks something like: BUG: spinlock recursion on CPU#3, swapper/3/0 lock: 0xffffff8a4bf29c80, .magic: dead4ead, .owner: swapper/3/0, .owner_cpu: 3 Hardware name: Qualcomm Technologies, Inc. Popsicle based on SM8850 (DT) Call trace: spin_bug+0x0 _raw_spin_lock_irqsave+0x80 hrtimer_try_to_cancel+0x94 task_contending+0x10c enqueue_dl_entity+0x2a4 dl_server_start+0x74 enqueue_task_fair+0x568 enqueue_task+0xac do_activate_task+0x14c ttwu_do_activate+0xcc try_to_wake_up+0x6c8 default_wake_function+0x20 autoremove_wake_function+0x1c __wake_up+0xac wakeup_kswapd+0x19c wake_all_kswapds+0x78 __alloc_pages_slowpath+0x1ac __alloc_pages_noprof+0x298 stack_depot_save_flags+0x6b0 stack_depot_save+0x14 set_track_prepare+0x5c ___slab_alloc+0xccc __kmalloc_cache_noprof+0x470 __set_page_owner+0x2bc post_alloc_hook[jt]+0x1b8 prep_new_page+0x28 get_page_from_freelist+0x1edc __alloc_pages_noprof+0x13c alloc_slab_page+0x244 allocate_slab+0x7c ___slab_alloc+0x8e8 kmem_cache_alloc_noprof+0x450 debug_objects_fill_pool+0x22c debug_object_activate+0x40 enqueue_hrtimer[jt]+0xdc hrtimer_start_range_ns+0x5f8 ...
CVSS v3.1
Score 5.5medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2025-39843 is a vulnerability in the Linux kernel's memory management (mm) subsystem, specifically in the slub allocator, where the wake up of the kswapd process in set_track_prepare is avoided to mitigate the issue. Red Hat has released a security update for Red Hat Enterprise Linux 9 to address this vulnerability. The advisory rates the impact as moderate and requires a system reboot after applying the update. No CVSS score is provided in the advisory. The vulnerability is tracked under CWE-833.
Potential Impact
The vulnerability affects the Linux kernel memory management subsystem and could potentially impact system stability or performance related to memory management. The exact impact details are not provided, but Red Hat rates this as a moderate security issue. There are no known exploits in the wild at this time.
Mitigation Recommendations
Red Hat has released an official security update for Red Hat Enterprise Linux 9 that addresses CVE-2025-39843. Users should apply the kernel update as described in the Red Hat advisory RHSA-2025:21926 and reboot their systems to ensure the fix takes effect. Patch status is confirmed as an official fix available from Red Hat.
Technical Details
- Gcve Source
- db.gcve.eu
- Csaf Category
- csaf_security_advisory
- Csaf Version
- 2.0
- Publisher
- Red Hat Product Security
- Advisory Id
- RHSA-2025:21926
- Cve Count
- 1
Threat ID: 6a3da1db4853345fc18291b3
Added to database: 06/25/2026, 21:47:07 UTC
Last enriched: 06/25/2026, 22:20:59 UTC
Last updated: 09/10/2026, 19:36:50 UTC
Views: 21
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