{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-98939",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2026-09-25T10:25:14.381Z",
        "datePublished": "2026-10-23T12:12:06.180Z",
        "dateUpdated": "2026-10-23T12:12:06.180Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-10-23T12:12:06.180Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "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. ]"
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "arch/x86/mm/pgtable.c"
                    ],
                    "versions": [
                        {
                            "version": "e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab",
                            "lessThan": "d3c2d2692bdf4af94bb27bc7a3aa0a348a567606",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "cc73b2043d106b467accd38e9b1fc09e0607c056",
                            "lessThan": "f38c57a28ebbd057471573e39555d5aa11ab03cf",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "d5d8b8662e6e5a565b47a0388640e88402f23274",
                            "lessThan": "e3ee38c1bc0b11a8d3e63dce7050759b61864286",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                },
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "arch/x86/mm/pgtable.c"
                    ],
                    "versions": [
                        {
                            "version": "6.18.53",
                            "lessThan": "6.18.56",
                            "status": "affected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2.7",
                            "lessThan": "7.2.10",
                            "status": "affected",
                            "versionType": "semver"
                        }
                    ]
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "operator": "OR",
                            "negate": false,
                            "cpeMatch": [
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "6.18.53",
                                    "versionEndExcluding": "6.18.56"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "7.2.7",
                                    "versionEndExcluding": "7.2.10"
                                }
                            ]
                        }
                    ]
                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/d3c2d2692bdf4af94bb27bc7a3aa0a348a567606"
                },
                {
                    "url": "https://git.kernel.org/stable/c/f38c57a28ebbd057471573e39555d5aa11ab03cf"
                },
                {
                    "url": "https://git.kernel.org/stable/c/e3ee38c1bc0b11a8d3e63dce7050759b61864286"
                }
            ],
            "title": "x86/mm: Drop unnecessary PMD page copy when freeing",
            "x_generator": {
                "engine": "bippy-1.2.0"
            }
        }
    }
}