# CVE-2025-38029: kasan: avoid sleepable page allocation from atomic context

CVE-2025-38029 is fixed in linux on 1 platform, first by DEBIAN-CVE-2025-38029, released June 18, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-38029
- Priority: Routine
- CVSS: 5.5 (Low)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 18, 2025
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-38029

## Description

In the Linux kernel, the following vulnerability has been resolved:  kasan: avoid sleepable page allocation from atomic context  apply_to_pte_range() enters the lazy MMU mode and then invokes kasan_populate_vmalloc_pte() callback on each page table walk iteration.  However, the callback can go into sleep when trying to allocate a single page, e.g.  if an architecutre disables preemption on lazy MMU mode enter.  On s390 if make arch_enter_lazy_mmu_mode() -> preempt_enable() and arch_leave_lazy_mmu_mode() -> preempt_disable(), such crash occurs:  [    0.663336] BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:321 [    0.663348] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2, name: kthreadd [    0.663358] preempt_count: 1, expected: 0 [    0.663366] RCU nest depth: 0, expected: 0 [    0.663375] no locks held by kthreadd/2. [    0.663383] Preemption disabled at: [    0.663386] [<0002f3284cbb4eda>] apply_to_pte_range+0xfa/0x4a0 [    0.663405] CPU: 0 UID: 0 PID: 2 Comm: kthreadd Not tainted 6.15.0-rc5-gcc-kasan-00043-gd76bb1ebb558-dirty #162 PREEMPT [    0.663408] Hardware name: IBM 3931 A01 701 (KVM/Linux) [    0.663409] Call Trace: [    0.663410]  [<0002f3284c385f58>] dump_stack_lvl+0xe8/0x140 [    0.663413]  [<0002f3284c507b9e>] __might_resched+0x66e/0x700 [    0.663415]  [<0002f3284cc4f6c0>] __alloc_frozen_pages_noprof+0x370/0x4b0 [    0.663419]  [<0002f3284ccc73c0>] alloc_pages_mpol+0x1a0/0x4a0 [    0.663421]  [<0002f3284ccc8518>] alloc_frozen_pages_noprof+0x88/0xc0 [    0.663424]  [<0002f3284ccc8572>] alloc_pages_noprof+0x22/0x120 [    0.663427]  [<0002f3284cc341ac>] get_free_pages_noprof+0x2c/0xc0 [    0.663429]  [<0002f3284cceba70>] kasan_populate_vmalloc_pte+0x50/0x120 [    0.663433]  [<0002f3284cbb4ef8>] apply_to_pte_range+0x118/0x4a0 [    0.663435]  [<0002f3284cbc7c14>] apply_to_pmd_range+0x194/0x3e0 [    0.663437]  [<0002f3284cbc99be>] __apply_to_page_range+0x2fe/0x7a0 [    0.663440]  [<0002f3284cbc9e88>] apply_to_page_range+0x28/0x40 [    0.663442]  [<0002f3284ccebf12>] kasan_populate_vmalloc+0x82/0xa0 [    0.663445]  [<0002f3284cc1578c>] alloc_vmap_area+0x34c/0xc10 [    0.663448]  [<0002f3284cc1c2a6>] __get_vm_area_node+0x186/0x2a0 [    0.663451]  [<0002f3284cc1e696>] __vmalloc_node_range_noprof+0x116/0x310 [    0.663454]  [<0002f3284cc1d950>] __vmalloc_node_noprof+0xd0/0x110 [    0.663457]  [<0002f3284c454b88>] alloc_thread_stack_node+0xf8/0x330 [    0.663460]  [<0002f3284c458d56>] dup_task_struct+0x66/0x4d0 [    0.663463]  [<0002f3284c45be90>] copy_process+0x280/0x4b90 [    0.663465]  [<0002f3284c460940>] kernel_clone+0xd0/0x4b0 [    0.663467]  [<0002f3284c46115e>] kernel_thread+0xbe/0xe0 [    0.663469]  [<0002f3284c4e440e>] kthreadd+0x50e/0x7f0 [    0.663472]  [<0002f3284c38c04a>] __ret_from_fork+0x8a/0xf0 [    0.663475]  [<0002f3284ed57ff2>] ret_from_fork+0xa/0x38  Instead of allocating single pages per-PTE, bulk-allocate the shadow memory prior to applying kasan_populate_vmalloc_pte() callback on a page range.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2025-38029](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38029.md) | Jun 18, 2025 |
| Linux | linux Debian 14 | 6.16.3-1 | [DEBIAN-CVE-2025-38029](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38029.md) | Jun 18, 2025 |

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