CVE-2026-98537

In the Linux kernel, the following vulnerability has been resolved:

workqueue: Fix NULL current_pwq deref in flush dependency check

check_flush_dependency() uses current_wq_worker() to determine whether the caller is a workqueue worker and then dereferences worker->current_pwq to test whether the current workqueue is WQ_MEM_RECLAIM.

current_wq_worker() only means that %current has PF_WQ_WORKER set. A kworker can reach check_flush_dependency() while it is not executing a work item. One such path is worker_thread() acting as the pool manager, where create_worker() does GFP_KERNEL allocation and the allocation path invokes the OOM notifier. In that state worker->current_pwq is NULL because current_pwq is set only by process_one_work() and cleared again after the work function returns.

[ 416.760634][ T375] Call trace: [ 416.760638][ T375] check_flush_dependency+0x80/0x120 (P) [ 416.760648][ T375] __flush_work+0x98/0x224 [ 416.760657][ T375] flush_work+0x30/0x44 [ 416.760665][ T375] … [ 416.760710][ T375] blocking_notifier_call_chain+0x58/0xa0 [ 416.760719][ T375] out_of_memory+0xb4/0x458 [ 416.760730][ T375] __alloc_pages_may_oom+0x11c/0x1a8 [ 416.760739][ T375] __alloc_pages_slowpath+0x314/0x46c [ 416.760746][ T375] __alloc_frozen_pages_noprof+0x110/0x1a4 [ 416.760753][ T375] new_slab+0x12c/0x484 [ 416.760759][ T375] ___slab_alloc+0x7a8/0xc7c [ 416.760765][ T375] __slab_alloc+0x74/0xd8 [ 416.760772][ T375] __kmalloc_cache_node_noprof+0x2ac/0x304 [ 416.760779][ T375] alloc_worker+0x28/0x60 [ 416.760785][ T375] create_worker+0x4c/0x20c [ 416.760790][ T375] worker_thread+0xe8/0x2b8 [ 416.760796][ T375] kthread+0x1a8/0x200 [ 416.760805][ T375] ret_from_fork+0x10/0x20

Guard the WQ_MEM_RECLAIM-worker warning with worker->current_pwq. If the kworker is not currently executing a work item, there is no current workqueue to diagnose with that warning. The PF_MEMALLOC warning is left unchanged so explicit reclaim context flushing a !WQ_MEM_RECLAIM target is still reported.

Affected Software

References

• https://git.kernel.org/stable/c/0c6b9b1e295aeff1132ac7aa738148cc65f06485
• https://git.kernel.org/stable/c/1dccf5dc2f8fe688270b261ca4216e03c6a1e674
• https://git.kernel.org/stable/c/513121e69388604619ea8c0ee07e86a3d1b5b5dc
• https://git.kernel.org/stable/c/8ffececcb88262389b4f91fed0fe4884b68204bc
• https://git.kernel.org/stable/c/9bb739a5c5a570c28a62afb98e9326e2a49743c1
• https://git.kernel.org/stable/c/cc190a6a1d20b87e6a9435202fc2a3bd84c79fb3
• https://git.kernel.org/stable/c/db6365ced4d5855e321f772b240c0e473bcfcdd5
• https://git.kernel.org/stable/c/f97e6d0572d1b39998e053732332bc3cfdd0b9aa