{"cve":"CVE-2025-22034","nvd":{"published":"2025-04-16T15:15:56.013","modified":"2026-07-30T06:22:04.373","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/gup: reject FOLL_SPLIT_PMD with hugetlb VMAs\n\nPatch series \"mm: fixes for device-exclusive entries (hmm)\", v2.\n\nDiscussing the PageTail() call in make_device_exclusive_range() with\nWilly, I recently discovered [1] that device-exclusive handling does not\nproperly work with THP, making the hmm-tests selftests fail if THPs are\nenabled on the system.\n\nLooking into more details, I found that hugetlb is not properly fenced,\nand I realized that something that was bugging me for longer -- how\ndevice-exclusive entries interact with mapcounts -- completely breaks\nmigration/swapout/split/hwpoison handling of these folios while they have\ndevice-exclusive PTEs.\n\nThe program below can be used to allocate 1 GiB worth of pages and making\nthem device-exclusive on a kernel with CONFIG_TEST_HMM.\n\nOnce they are device-exclusive, these folios cannot get swapped out\n(proc$pid/smaps_rollup will always indicate 1 GiB RSS no matter how much\none forces memory reclaim), and when having a memory block onlined to\nZONE_MOVABLE, trying to offline it will loop forever and complain about\nfailed migration of a page that should be movable.\n\n# echo offline > /sys/devices/system/memory/memory136/state\n# echo online_movable > /sys/devices/system/memory/memory136/state\n# ./hmm-swap &\n... wait until everything is device-exclusive\n# echo offline > /sys/devices/system/memory/memory136/state\n[  285.193431][T14882] page: refcount:2 mapcount:0 mapping:0000000000000000\n  index:0x7f20671f7 pfn:0x442b6a\n[  285.196618][T14882] memcg:ffff888179298000\n[  285.198085][T14882] anon flags: 0x5fff0000002091c(referenced|uptodate|\n  dirty|active|owner_2|swapbacked|node=1|zone=3|lastcpupid=0x7ff)\n[  285.201734][T14882] raw: ...\n[  285.204464][T14882] raw: ...\n[  285.207196][T14882] page dumped because: migration failure\n[  285.209072][T14882] page_owner tracks the page as allocated\n[  285.210915][T14882] page last allocated via order 0, migratetype\n  Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO),\n  id 14926, tgid 14926 (hmm-swap), ts 254506295376, free_ts 227402023774\n[  285.216765][T14882]  post_alloc_hook+0x197/0x1b0\n[  285.218874][T14882]  get_page_from_freelist+0x76e/0x3280\n[  285.220864][T14882]  __alloc_frozen_pages_noprof+0x38e/0x2740\n[  285.223302][T14882]  alloc_pages_mpol+0x1fc/0x540\n[  285.225130][T14882]  folio_alloc_mpol_noprof+0x36/0x340\n[  285.227222][T14882]  vma_alloc_folio_noprof+0xee/0x1a0\n[  285.229074][T14882]  __handle_mm_fault+0x2b38/0x56a0\n[  285.230822][T14882]  handle_mm_fault+0x368/0x9f0\n...\n\nThis series fixes all issues I found so far.  There is no easy way to fix\nwithout a bigger rework/cleanup.  I have a bunch of cleanups on top (some\nprevious sent, some the result of the discussion in v1) that I will send\nout separately once this landed and I get to it.\n\nI wish we could just use some special present PROT_NONE PTEs instead of\nthese (non-present, non-none) fake-swap entries; but that just results in\nthe same problem we keep having (lack of spare PTE bits), and staring at\nother similar fake-swap entries, that ship has sailed.\n\nWith this series, make_device_exclusive() doesn't actually belong into\nmm/rmap.c anymore, but I'll leave moving that for another day.\n\nI only tested this series with the hmm-tests selftests due to lack of HW,\nso I'd appreciate some testing, especially if the interaction between two\nGPUs wanting a device-exclusive entry works as expected.\n\n<program>\n#include <stdio.h>\n#include <fcntl.h>\n#include <stdint.h>\n#include <unistd.h>\n#include <stdlib.h>\n#include <string.h>\n#include <sys/mman.h>\n#include <sys/ioctl.h>\n#include <linux/types.h>\n#include <linux/ioctl.h>\n\n#define HMM_DMIRROR_EXCLUSIVE _IOWR('H', 0x05, struct hmm_dmirror_cmd)\n\nstruct hmm_dmirror_cmd {\n\t__u64 addr;\n\t__u64 ptr;\n\t__u64 npages;\n\t__u64 cpages;\n\t__u64 faults;\n};\n\nconst size_t size = 1 * 1024 * 1024 * 1024ul;\nconst size_t chunk_size = 2 * 1024 * 1024ul;\n\nint m\n---truncated---","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/2e877ff3492267def06dd50cb165dc9ab8838e7d","https://git.kernel.org/stable/c/48d28417c66cce2f3b0ba773fcb6695a56eff220","https://git.kernel.org/stable/c/8977752c8056a6a094a279004a49722da15bace3","https://git.kernel.org/stable/c/fd900832e8440046627b60697687ab5d04398008"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:01:11.054312287+00:00"},"epss":{"cve":"CVE-2025-22034","score":0.00277,"percentile":0.20209,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}