CVE-2025-39843
Full vulnerability record from the local CVENow database.
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 ...
Severity
MEDIUM
CVSS score
5.5
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-09-19 16:15:43.047000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON
{
"id": "CVE-2025-39843",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-09-19T16:15:43.047",
"lastModified": "2026-10-19T21:10:00.160",
"vulnStatus": "Modified",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: slub: avoid wake up kswapd in set_track_prepare\n\nset_track_prepare() can incur lock recursion.\nThe issue is that it is called from hrtimer_start_range_ns\nholding the per_cpu(hrtimer_bases)[n].lock, but when enabled\nCONFIG_DEBUG_OBJECTS_TIMERS, may wake up kswapd in set_track_prepare,\nand try to hold the per_cpu(hrtimer_bases)[n].lock.\n\nAvoid deadlock caused by implicitly waking up kswapd by passing in\nallocation flags, which do not contain __GFP_KSWAPD_RECLAIM in the\ndebug_objects_fill_pool() case. Inside stack depot they are processed by\ngfp_nested_mask().\nSince ___slab_alloc() has preemption disabled, we mask out\n__GFP_DIRECT_RECLAIM from the flags there.\n\nThe oops looks something like:\n\nBUG: spinlock recursion on CPU#3, swapper/3/0\n lock: 0xffffff8a4bf29c80, .magic: dead4ead, .owner: swapper/3/0, .owner_cpu: 3\nHardware name: Qualcomm Technologies, Inc. Popsicle based on SM8850 (DT)\nCall trace:\nspin_bug+0x0\n_raw_spin_lock_irqsave+0x80\nhrtimer_try_to_cancel+0x94\ntask_contending+0x10c\nenqueue_dl_entity+0x2a4\ndl_server_start+0x74\nenqueue_task_fair+0x568\nenqueue_task+0xac\ndo_activate_task+0x14c\nttwu_do_activate+0xcc\ntry_to_wake_up+0x6c8\ndefault_wake_function+0x20\nautoremove_wake_function+0x1c\n__wake_up+0xac\nwakeup_kswapd+0x19c\nwake_all_kswapds+0x78\n__alloc_pages_slowpath+0x1ac\n__alloc_pages_noprof+0x298\nstack_depot_save_flags+0x6b0\nstack_depot_save+0x14\nset_track_prepare+0x5c\n___slab_alloc+0xccc\n__kmalloc_cache_noprof+0x470\n__set_page_owner+0x2bc\npost_alloc_hook[jt]+0x1b8\nprep_new_page+0x28\nget_page_from_freelist+0x1edc\n__alloc_pages_noprof+0x13c\nalloc_slab_page+0x244\nallocate_slab+0x7c\n___slab_alloc+0x8e8\nkmem_cache_alloc_noprof+0x450\ndebug_objects_fill_pool+0x22c\ndebug_object_activate+0x40\nenqueue_hrtimer[jt]+0xdc\nhrtimer_start_range_ns+0x5f8\n..."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nmm: slub: evitar despertar a kswapd en set_track_prepare\n\nset_track_prepare() puede incurrir en recursión de bloqueo.\nEl problema es que se llama desde hrtimer_start_range_ns manteniendo el per_cpu(hrtimer_bases)[n].lock, pero cuando se habilita CONFIG_DEBUG_OBJECTS_TIMERS, puede despertar a kswapd en set_track_prepare, e intentar mantener el per_cpu(hrtimer_bases)[n].lock.\n\nEvitar interbloqueo causado por despertar implícitamente a kswapd pasando banderas de asignación, que no contienen __GFP_KSWAPD_RECLAIM en el caso de debug_objects_fill_pool(). Dentro del stack depot son procesados por gfp_nested_mask().\nDado que ___slab_alloc() tiene la preemption deshabilitada, enmascaramos __GFP_DIRECT_RECLAIM de las banderas allí.\n\nEl oops se ve algo así como:\n\nBUG: recursión de spinlock en CPU#3, swapper/3/0\nlock: 0xffffff8a4bf29c80, .magic: dead4ead, .owner: swapper/3/0, .owner_cpu: 3\nNombre de hardware: Qualcomm Technologies, Inc. Popsicle basado en SM8850 (DT)\nRastro de llamada:\nspin_bug+0x0\n_raw_spin_lock_irqsave+0x80\nhrtimer_try_to_cancel+0x94\ntask_contending+0x10c\nenqueue_dl_entity+0x2a4\ndl_server_start+0x74\nenqueue_task_fair+0x568\nenqueue_task+0xac\ndo_activate_task+0x14c\nttwu_do_activate+0xcc\ntry_to_wake_up+0x6c8\ndefault_wake_function+0x20\nautoremove_wake_function+0x1c\n__wake_up+0xac\nwakeup_kswapd+0x19c\nwake_all_kswapds+0x78\n__alloc_pages_slowpath+0x1ac\n__alloc_pages_noprof+0x298\nstack_depot_save_flags+0x6b0\nstack_depot_save+0x14\nset_track_prepare+0x5c\n___slab_alloc+0xccc\n__kmalloc_cache_noprof+0x470\n__set_page_owner+0x2bc\npost_alloc_hook[jt]+0x1b8\nprep_new_page+0x28\nget_page_from_freelist+0x1edc\n__alloc_pages_noprof+0x13c\nalloc_slab_page+0x244\nallocate_slab+0x7c\n___slab_alloc+0x8e8\nkmem_cache_alloc_noprof+0x450\ndebug_objects_fill_pool+0x22c\ndebug_object_activate+0x40\nenqueue_hrtimer[jt]+0xdc\nhrtimer_start_range_ns+0x5f8\n..."
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