{"id":"DEBIAN-CVE-2025-22034","details":"In the Linux kernel, the following vulnerability has been resolved:  mm/gup: reject FOLL_SPLIT_PMD with hugetlb VMAs  Patch series \"mm: fixes for device-exclusive entries (hmm)\", v2.  Discussing the PageTail() call in make_device_exclusive_range() with Willy, I recently discovered [1] that device-exclusive handling does not properly work with THP, making the hmm-tests selftests fail if THPs are enabled on the system.  Looking into more details, I found that hugetlb is not properly fenced, and I realized that something that was bugging me for longer -- how device-exclusive entries interact with mapcounts -- completely breaks migration/swapout/split/hwpoison handling of these folios while they have device-exclusive PTEs.  The program below can be used to allocate 1 GiB worth of pages and making them device-exclusive on a kernel with CONFIG_TEST_HMM.  Once they are device-exclusive, these folios cannot get swapped out (proc$pid/smaps_rollup will always indicate 1 GiB RSS no matter how much one forces memory reclaim), and when having a memory block onlined to ZONE_MOVABLE, trying to offline it will loop forever and complain about failed migration of a page that should be movable.  # echo offline \u003e /sys/devices/system/memory/memory136/state # echo online_movable \u003e /sys/devices/system/memory/memory136/state # ./hmm-swap & ... wait until everything is device-exclusive # echo offline \u003e /sys/devices/system/memory/memory136/state [  285.193431][T14882] page: refcount:2 mapcount:0 mapping:0000000000000000   index:0x7f20671f7 pfn:0x442b6a [  285.196618][T14882] memcg:ffff888179298000 [  285.198085][T14882] anon flags: 0x5fff0000002091c(referenced|uptodate|   dirty|active|owner_2|swapbacked|node=1|zone=3|lastcpupid=0x7ff) [  285.201734][T14882] raw: ... [  285.204464][T14882] raw: ... [  285.207196][T14882] page dumped because: migration failure [  285.209072][T14882] page_owner tracks the page as allocated [  285.210915][T14882] page last allocated via order 0, migratetype   Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO),   id 14926, tgid 14926 (hmm-swap), ts 254506295376, free_ts 227402023774 [  285.216765][T14882]  post_alloc_hook+0x197/0x1b0 [  285.218874][T14882]  get_page_from_freelist+0x76e/0x3280 [  285.220864][T14882]  __alloc_frozen_pages_noprof+0x38e/0x2740 [  285.223302][T14882]  alloc_pages_mpol+0x1fc/0x540 [  285.225130][T14882]  folio_alloc_mpol_noprof+0x36/0x340 [  285.227222][T14882]  vma_alloc_folio_noprof+0xee/0x1a0 [  285.229074][T14882]  __handle_mm_fault+0x2b38/0x56a0 [  285.230822][T14882]  handle_mm_fault+0x368/0x9f0 ...  This series fixes all issues I found so far.  There is no easy way to fix without a bigger rework/cleanup.  I have a bunch of cleanups on top (some previous sent, some the result of the discussion in v1) that I will send out separately once this landed and I get to it.  I wish we could just use some special present PROT_NONE PTEs instead of these (non-present, non-none) fake-swap entries; but that just results in the same problem we keep having (lack of spare PTE bits), and staring at other similar fake-swap entries, that ship has sailed.  With this series, make_device_exclusive() doesn't actually belong into mm/rmap.c anymore, but I'll leave moving that for another day.  I only tested this series with the hmm-tests selftests due to lack of HW, so I'd appreciate some testing, especially if the interaction between two GPUs wanting a device-exclusive entry works as expected.  \u003cprogram\u003e #include \u003cstdio.h\u003e #include \u003cfcntl.h\u003e #include \u003cstdint.h\u003e #include \u003cunistd.h\u003e #include \u003cstdlib.h\u003e #include \u003cstring.h\u003e #include \u003csys/mman.h\u003e #include \u003csys/ioctl.h\u003e #include \u003clinux/types.h\u003e #include \u003clinux/ioctl.h\u003e  #define HMM_DMIRROR_EXCLUSIVE _IOWR('H', 0x05, struct hmm_dmirror_cmd)  struct hmm_dmirror_cmd { \t__u64 addr; \t__u64 ptr; \t__u64 npages; \t__u64 cpages; \t__u64 faults; };  const size_t size = 1 * 1024 * 1024 * 1024ul; const size_t chunk_size = 2 * 1024 * 1024ul;  int m ---truncated---","modified":"2026-08-27T23:05:13.693677678Z","published":"2025-04-16T15:15:56.013Z","upstream":["CVE-2025-22034"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-22034"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.25-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-22034.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.25-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-22034.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}