CVE-2025-39845
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel, ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() were defined to ensure proper page table synchronization when calling p*d_populate_kernel(). The fix addresses intermittent boot failures on systems with 4-level paging and large persistent memory, as well as a crash in vmemmap_set_pmd() caused by accessing vmemmap before sync_global_pgds().
Risk Assessment
Lack of page table synchronization can cause kernel panics during initialization of persistent memory or devices like GPUs, leading to service disruption and potential data loss.
Recommendation
Immediately update the Linux kernel to a version containing this patch (e.g., 6.14.x or later), especially on systems with large persistent memory or those using vmemmap-mapped memory.
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In the Linux kernel powerpc/pseries papr-phy-attest, missing validation of cmd.length could lead to buffer overflow. The fix adds length checks and fixes memory leaks on error paths.
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In the Linux kernel, the xcrb_msg_to_type6cprb_msgx() and xcrb_msg_to_type6_ep11cprb_msgx() functions for s390/zcrypt copy a user space message into a kernel buffer based on length, but further processing assumes 4-byte alignment. As a result, up to 3 bytes of uninitialized kernel memory are forwarded to further processing, potentially exposing kernel memory to the crypto card firmware.
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In the Linux kernel XFS filesystem, during AGI repair, the function xrep_iunlink_walk_ondisk_bucket may attempt to use the pointer sc->sa.agi_bp, which can be null if the buffer verifier fails. The fix uses ragi->agi_bp instead, which skips verifier checks, to avoid walking off the end of memory.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: x86/mm/64: define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() Define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() to ensure page tables are properly synchronized when calling p*d_populate_kernel(). For 5-level paging, synchronization is performed via pgd_populate_kernel(). In 4-level paging, pgd_populate() is a no-op, so synchronization is instead performed at the P4D level via p4d_populate_kernel(). This fixes intermittent boot failures on systems using 4-level paging and a large amount of persistent memory: BUG: unable to handle page fault for address: ffffe70000000034 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI RIP: 0010:__init_single_page+0x9/0x6d Call Trace: <TASK> __init_zone_device_page+0x17/0x5d memmap_init_zone_device+0x154/0x1bb pagemap_range+0x2e0/0x40f memremap_pages+0x10b/0x2f0 devm_memremap_pages+0x1e/0x60 dev_dax_probe+0xce/0x2ec [device_dax] dax_bus_probe+0x6d/0xc9 [... snip ...] </TASK> It also fixes a crash in vmemmap_set_pmd() caused by accessing vmemmap before sync_global_pgds() [1]: BUG: unable to handle page fault for address: ffffeb3ff1200000 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: Oops: 0002 [#1] PREEMPT SMP NOPTI Tainted: [W]=WARN RIP: 0010:vmemmap_set_pmd+0xff/0x230 <TASK> vmemmap_populate_hugepages+0x176/0x180 vmemmap_populate+0x34/0x80 __populate_section_memmap+0x41/0x90 sparse_add_section+0x121/0x3e0 __add_pages+0xba/0x150 add_pages+0x1d/0x70 memremap_pages+0x3dc/0x810 devm_memremap_pages+0x1c/0x60 xe_devm_add+0x8b/0x100 [xe] xe_tile_init_noalloc+0x6a/0x70 [xe] xe_device_probe+0x48c/0x740 [xe] [... snip ...]

