{"api_version":"1","generated_at":"2026-07-04T14:08:18+00:00","cve":"CVE-2026-53155","urls":{"html":"https://cve.report/CVE-2026-53155","api":"https://cve.report/api/cve/CVE-2026-53155.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-53155","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-53155"},"summary":{"title":"mm/huge_memory: use correct flags for device private PMD entry","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: use correct flags for device private PMD entry\n\nCommit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") updated set_pmd_migration_entry() to use\npmdp_huge_get_and_clear() in the softleaf case, but made no further\nadjustments to the function itself.\n\nTherefore this function continues to incorrectly use pmd_write(),\npmd_soft_dirty() and pmd_uffd_wp() to determine whether the installed\nmigration entry should be marked writable, softdirty or uffd-wp\nrespectively.\n\nWhilst all are incorrect, the most problematic of these is pmd_write(), as\nthis can lead to corrupted rmap state.\n\nOn x86-64 _PAGE_SWP_SOFT_DIRTY is aliased to _PAGE_RW.  So calling\npmd_write() on a softleaf will return the softdirty state encoded in the\nentry, assuming CONFIG_MEM_SOFT_DIRTY was enabled.\n\nThis was observed when running the hmm.hmm_device_private.anon_write_child\nselftest:\n\n1. The test faults in a range then migrates it such that a device-private\n   THP range is established.\n\n2. The parent then migrates it to a device-private writable PMD entry whose\n   folio is entirely AnonExclusive with entire_mapcount=1, softdirty set\n   (accidentally correct write state).\n\n3. The parent forks and the PMD entries are set to device-private read only\n   entries, entire_mapcount=2, softdirty still set.\n\n4. [BUG] The child writes to the range then migrates to RAM - intending to\n   install non-writable migration entries - but replacing parent and child\n   PMD mappings with WRITABLE entries due to misinterpreting the softdirty\n   bit.\n\n5. In remove_migration_pmd(), if !softleaf_is_migration_read(entry) we\n   set the RMAP_EXCLUSIVE flag when calling folio_add_anon_rmap_pmd() for\n   both parent and child, which are therefore AnonExclusive.\n\n6. [SPLAT] Child sets migrated folio entire_mapcount=1, parent sets\n   entire_mapcount=2 and we end up with an AnonExclusive folio with\n   entire_mapcount=2! Assert fires in __folio_add_anon_rmap():\n\n\t\tVM_WARN_ON_FOLIO(folio_test_large(folio) &&\n\t\t\t\t folio_entire_mapcount(folio) > 1 &&\n\t\t\t\t PageAnonExclusive(cur_page), folio)\n\nThis patch fixes the issue by correctly referencing the softleaf entry\nfields for writable, softdirty and uffd-wp in set_pmd_migration_entry().\n\nIt also only updates A/D flags if the entry is present as these are\notherwise not meaningful for a softleaf entry.\n\nThis patch also flips the if (!present) { ...  } else { ...  } logic in\nset_pmd_migration_entry() so it is easier to understand, and adds some\ncomments to make things clearer.\n\nI was able to bisect this to commit 775465fd26a3 (\"lib/test_hmm: add zone\ndevice private THP test infrastructure\") which first exposes this bug as\nit was the commit that permitted test_hmm to generate the test.\n\nHowever commit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") is the commit that actually enabled this\nbehaviour.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-06-25 09:16:32","updated_at":"2026-06-30 14:44:27"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/d7251c8d3f7cea76543abac6cf4ed15582c10846","name":"https://git.kernel.org/stable/c/d7251c8d3f7cea76543abac6cf4ed15582c10846","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/43e7f189769c512c843184a8a5892ac779a6bd90","name":"https://git.kernel.org/stable/c/43e7f189769c512c843184a8a5892ac779a6bd90","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-53155","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53155","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 65edfda6f3f2e58f757485a056e4f1775a1404a8 d7251c8d3f7cea76543abac6cf4ed15582c10846 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 65edfda6f3f2e58f757485a056e4f1775a1404a8 43e7f189769c512c843184a8a5892ac779a6bd90 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.19","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.13 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"53155","cve":"CVE-2026-53155","epss":"0.001720000","percentile":"0.068870000","score_date":"2026-07-03","updated_at":"2026-07-04 00:02:19"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["mm/huge_memory.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"d7251c8d3f7cea76543abac6cf4ed15582c10846","status":"affected","version":"65edfda6f3f2e58f757485a056e4f1775a1404a8","versionType":"git"},{"lessThan":"43e7f189769c512c843184a8a5892ac779a6bd90","status":"affected","version":"65edfda6f3f2e58f757485a056e4f1775a1404a8","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["mm/huge_memory.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.19"},{"lessThan":"6.19","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"7.0.*","status":"unaffected","version":"7.0.13","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0.13","versionStartIncluding":"6.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1","versionStartIncluding":"6.19","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: use correct flags for device private PMD entry\n\nCommit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") updated set_pmd_migration_entry() to use\npmdp_huge_get_and_clear() in the softleaf case, but made no further\nadjustments to the function itself.\n\nTherefore this function continues to incorrectly use pmd_write(),\npmd_soft_dirty() and pmd_uffd_wp() to determine whether the installed\nmigration entry should be marked writable, softdirty or uffd-wp\nrespectively.\n\nWhilst all are incorrect, the most problematic of these is pmd_write(), as\nthis can lead to corrupted rmap state.\n\nOn x86-64 _PAGE_SWP_SOFT_DIRTY is aliased to _PAGE_RW.  So calling\npmd_write() on a softleaf will return the softdirty state encoded in the\nentry, assuming CONFIG_MEM_SOFT_DIRTY was enabled.\n\nThis was observed when running the hmm.hmm_device_private.anon_write_child\nselftest:\n\n1. The test faults in a range then migrates it such that a device-private\n   THP range is established.\n\n2. The parent then migrates it to a device-private writable PMD entry whose\n   folio is entirely AnonExclusive with entire_mapcount=1, softdirty set\n   (accidentally correct write state).\n\n3. The parent forks and the PMD entries are set to device-private read only\n   entries, entire_mapcount=2, softdirty still set.\n\n4. [BUG] The child writes to the range then migrates to RAM - intending to\n   install non-writable migration entries - but replacing parent and child\n   PMD mappings with WRITABLE entries due to misinterpreting the softdirty\n   bit.\n\n5. In remove_migration_pmd(), if !softleaf_is_migration_read(entry) we\n   set the RMAP_EXCLUSIVE flag when calling folio_add_anon_rmap_pmd() for\n   both parent and child, which are therefore AnonExclusive.\n\n6. [SPLAT] Child sets migrated folio entire_mapcount=1, parent sets\n   entire_mapcount=2 and we end up with an AnonExclusive folio with\n   entire_mapcount=2! Assert fires in __folio_add_anon_rmap():\n\n\t\tVM_WARN_ON_FOLIO(folio_test_large(folio) &&\n\t\t\t\t folio_entire_mapcount(folio) > 1 &&\n\t\t\t\t PageAnonExclusive(cur_page), folio)\n\nThis patch fixes the issue by correctly referencing the softleaf entry\nfields for writable, softdirty and uffd-wp in set_pmd_migration_entry().\n\nIt also only updates A/D flags if the entry is present as these are\notherwise not meaningful for a softleaf entry.\n\nThis patch also flips the if (!present) { ...  } else { ...  } logic in\nset_pmd_migration_entry() so it is easier to understand, and adds some\ncomments to make things clearer.\n\nI was able to bisect this to commit 775465fd26a3 (\"lib/test_hmm: add zone\ndevice private THP test infrastructure\") which first exposes this bug as\nit was the commit that permitted test_hmm to generate the test.\n\nHowever commit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") is the commit that actually enabled this\nbehaviour."}],"providerMetadata":{"dateUpdated":"2026-06-25T08:38:38.828Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/d7251c8d3f7cea76543abac6cf4ed15582c10846"},{"url":"https://git.kernel.org/stable/c/43e7f189769c512c843184a8a5892ac779a6bd90"}],"title":"mm/huge_memory: use correct flags for device private PMD entry","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-53155","datePublished":"2026-06-25T08:38:38.828Z","dateReserved":"2026-06-09T07:44:35.388Z","dateUpdated":"2026-06-25T08:38:38.828Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-06-25 09:16:32","lastModifiedDate":"2026-06-30 14:44:27","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"53155","Ordinal":"1","Title":"mm/huge_memory: use correct flags for device private PMD entry","CVE":"CVE-2026-53155","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"53155","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: use correct flags for device private PMD entry\n\nCommit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") updated set_pmd_migration_entry() to use\npmdp_huge_get_and_clear() in the softleaf case, but made no further\nadjustments to the function itself.\n\nTherefore this function continues to incorrectly use pmd_write(),\npmd_soft_dirty() and pmd_uffd_wp() to determine whether the installed\nmigration entry should be marked writable, softdirty or uffd-wp\nrespectively.\n\nWhilst all are incorrect, the most problematic of these is pmd_write(), as\nthis can lead to corrupted rmap state.\n\nOn x86-64 _PAGE_SWP_SOFT_DIRTY is aliased to _PAGE_RW.  So calling\npmd_write() on a softleaf will return the softdirty state encoded in the\nentry, assuming CONFIG_MEM_SOFT_DIRTY was enabled.\n\nThis was observed when running the hmm.hmm_device_private.anon_write_child\nselftest:\n\n1. The test faults in a range then migrates it such that a device-private\n   THP range is established.\n\n2. The parent then migrates it to a device-private writable PMD entry whose\n   folio is entirely AnonExclusive with entire_mapcount=1, softdirty set\n   (accidentally correct write state).\n\n3. The parent forks and the PMD entries are set to device-private read only\n   entries, entire_mapcount=2, softdirty still set.\n\n4. [BUG] The child writes to the range then migrates to RAM - intending to\n   install non-writable migration entries - but replacing parent and child\n   PMD mappings with WRITABLE entries due to misinterpreting the softdirty\n   bit.\n\n5. In remove_migration_pmd(), if !softleaf_is_migration_read(entry) we\n   set the RMAP_EXCLUSIVE flag when calling folio_add_anon_rmap_pmd() for\n   both parent and child, which are therefore AnonExclusive.\n\n6. [SPLAT] Child sets migrated folio entire_mapcount=1, parent sets\n   entire_mapcount=2 and we end up with an AnonExclusive folio with\n   entire_mapcount=2! Assert fires in __folio_add_anon_rmap():\n\n\t\tVM_WARN_ON_FOLIO(folio_test_large(folio) &&\n\t\t\t\t folio_entire_mapcount(folio) > 1 &&\n\t\t\t\t PageAnonExclusive(cur_page), folio)\n\nThis patch fixes the issue by correctly referencing the softleaf entry\nfields for writable, softdirty and uffd-wp in set_pmd_migration_entry().\n\nIt also only updates A/D flags if the entry is present as these are\notherwise not meaningful for a softleaf entry.\n\nThis patch also flips the if (!present) { ...  } else { ...  } logic in\nset_pmd_migration_entry() so it is easier to understand, and adds some\ncomments to make things clearer.\n\nI was able to bisect this to commit 775465fd26a3 (\"lib/test_hmm: add zone\ndevice private THP test infrastructure\") which first exposes this bug as\nit was the commit that permitted test_hmm to generate the test.\n\nHowever commit 65edfda6f3f2 (\"mm/rmap: extend rmap and migration support\ndevice-private entries\") is the commit that actually enabled this\nbehaviour.","Type":"Description","Title":"mm/huge_memory: use correct flags for device private PMD entry"}]}}}