{"id":"CVE-2026-98939","revision":null,"records":[{"revision":"78183c40e1164aff848e14d3418991f4","observedAt":"2026-10-23T16:01:20.601+00:00","statement":{"source":"cve-program","id":"CVE-2026-98939","aliases":[],"title":"x86/mm: Drop unnecessary PMD page copy when freeing","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm: Drop unnecessary PMD page copy when freeing\n\nOn a box with a discrete GPU, lockdep reports a possible deadlock as\nsoon as kswapd shrinks the TTM page pool. The immediate cause is an\nx86 commit that added an mmap_read_lock() to kernel page protection\nmunging code.\n\nThe huge vmap code holds the same lock over a GFP_KERNEL allocation,\nwhich is a no-no now that reclaim can take it. That allocation is in a\npage table *free* path and ends up being for dubious purposes[1].\nBasically, it tries to avoid hardware setting Accessed=1 in page table\nentries that are unreachable by the hardware, a non-issue.\n\nRemove the PMD copy. Detach the original PMD page at the PUD, flush\nthe mid-level caches, and free the PTE tables straight from the\ndetached PMD page. With no allocation left, the locking issue is gone.\n\nLockdep splat/analysis:\n\n  WARNING: possible circular locking dependency detected\n  7.3.0-rc3-f6e7b42bf05b+ #183 Tainted: G     U\n  ------------------------------------------------------\n  kswapd0/269 is trying to acquire lock:\n  ((init_mm).mmap_lock){++++}-{4:4}, at: change_page_attr_set_clr+0x29a/0x4a0\n  but task is already holding lock:\n  (pool_shrink_rwsem){.+.+}-{4:4}, at: ttm_pool_shrink+0xb2/0x330 [ttm]\n  Chain exists of:\n    (init_mm).mmap_lock --> fs_reclaim --> pool_shrink_rwsem\n\nThe cycle is built from three edges:\n\n  1) pool_shrink_rwsem -> (init_mm).mmap_lock\n\n     The TTM shrinker restores the caching attribute of every page it\n     frees, while holding pool_shrink_rwsem:\n\n       ttm_pool_shrink()\n       -> ttm_pool_dispose_list()\n       -> ttm_pool_free_page()\n       -> set_pages_wb()\n       -> change_page_attr_set_clr()   [ init_mm mmap read lock ]\n\n  2) fs_reclaim -> pool_shrink_rwsem\n\n     The same shrinker, called from reclaim.\n\n  3) (init_mm).mmap_lock -> fs_reclaim\n\n     ioremap() installing a huge PUD mapping over an existing PMD table:\n\n       ioremap_page_range()\n       -> vmap_range_noflush()\n       -> vmap_try_huge_pud()          [ init_mm mmap read lock ]\n       -> pud_free_pmd_page()\n       -> __get_free_page(GFP_KERNEL)  [ enters reclaim ]\n\n[ dhansen: Lots of changelog munging/trimming and merged comments from my\n\t   version of the fix. ]","state":0,"publishedAt":"2026-10-23T12:12:06.18+00:00","modifiedAt":"2026-10-23T12:12:06.18+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"arch/x86/mm/pgtable.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab\",\n                            \"lessThan\": \"d3c2d2692bdf4af94bb27bc7a3aa0a348a567606\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"cc73b2043d106b467accd38e9b1fc09e0607c056\",\n                            \"lessThan\": \"f38c57a28ebbd057471573e39555d5aa11ab03cf\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"d5d8b8662e6e5a565b47a0388640e88402f23274\",\n                            \"lessThan\": \"e3ee38c1bc0b11a8d3e63dce7050759b61864286\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"arch/x86/mm/pgtable.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.18.53\",\n                            \"lessThan\": \"6.18.56\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.7\",\n                            \"lessThan\": \"7.2.10\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/d3c2d2692bdf4af94bb27bc7a3aa0a348a567606","https://git.kernel.org/stable/c/f38c57a28ebbd057471573e39555d5aa11ab03cf","https://git.kernel.org/stable/c/e3ee38c1bc0b11a8d3e63dce7050759b61864286"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98939","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98939","identifiers":["CVE-2026-98939"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-1de1564061e94716a5c6ac7e9c6f3013","complete":false,"records":11690,"lastAttemptAt":"2026-10-28T07:20:12.9404081+00:00","lastSuccessAt":"2026-10-28T07:20:12.936+00:00","error":"18 identifier lookups failed; latest failures include HTTP 403. Other identifiers were checked independently.","lastVerifiedAt":"2026-10-28T07:20:12.936+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":6982,"expectedIdentifiers":13514,"failedIdentifiers":18},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. Not a global EPSS backfill.","generation":"2026-10-28T07:08:14.3778977+00:00","complete":true,"records":1093,"lastAttemptAt":"2026-10-28T07:08:14.3778977+00:00","lastSuccessAt":"2026-10-28T07:08:14.5500766+00:00","error":null,"lastVerifiedAt":"2026-10-28T07:08:14.550077+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"nvd","scope":"Rolling NVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global NVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-8d16a738328646698f9217d8ea11893c","complete":true,"records":13449,"lastAttemptAt":"2026-10-28T07:08:15.0871785+00:00","lastSuccessAt":"2026-10-27T22:48:29.491+00:00","error":null,"lastVerifiedAt":"2026-10-27T22:48:29.491+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13514,"expectedIdentifiers":13514,"failedIdentifiers":0},{"source":"osv:Go","scope":"Complete OSV Go ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"go-f7cb12508d9e6a348c8a60f772ed85529cc80cd2ff853da1099b57754b20e943","complete":true,"records":9790,"lastAttemptAt":"2026-10-28T07:08:14.232626+00:00","lastSuccessAt":"2026-10-27T21:49:03.9756799+00:00","error":null,"lastVerifiedAt":"2026-10-28T07:08:14.232626+00:00","snapshotPublishedAt":"2026-10-27T21:48:11+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:NuGet","scope":"Complete OSV NuGet ecosystem archive, including GitHub Advisory Database records; NuGet version matching only","generation":"nuget-72e5e79de0026dd0562d40734074a2236a06886643d67182b8381eaee757dbf7","complete":true,"records":1966,"lastAttemptAt":"2026-10-28T07:06:21.7385741+00:00","lastSuccessAt":"2026-10-27T21:46:38.0277323+00:00","error":null,"lastVerifiedAt":"2026-10-28T07:06:21.7385741+00:00","snapshotPublishedAt":"2026-10-27T21:18:15+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:crates.io","scope":"Complete OSV crates.io ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"crates.io-3a5b306d60fc44677a03a8afc99d87e6c5402770ef68d560f94a8c3ad3802b75","complete":true,"records":3001,"lastAttemptAt":"2026-10-28T07:08:14.3365383+00:00","lastSuccessAt":"2026-10-27T16:45:49.0050993+00:00","error":null,"lastVerifiedAt":"2026-10-28T07:08:14.3365383+00:00","snapshotPublishedAt":"2026-10-27T16:33:43+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:npm","scope":"Complete OSV npm ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"npm-cf3d7f231228fbafaf00b899a3529c24d9add8aab904e519be8d085668fa0c9c","complete":true,"records":230856,"lastAttemptAt":"2026-10-28T07:08:14.1053593+00:00","lastSuccessAt":"2026-10-28T07:08:12.8687117+00:00","error":null,"lastVerifiedAt":"2026-10-28T07:08:14.1053593+00:00","snapshotPublishedAt":"2026-10-28T06:48:05+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null}]}