{"id":"CVE-2026-93066","revision":"e3bce6f6f19b4e5c934240d20a7c5caf","records":[{"revision":"e3bce6f6f19b4e5c934240d20a7c5caf","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-93066","aliases":[],"title":"x86/mm/pat: Take cpa_lock around large-page collapse","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/mm/pat: Take cpa_lock around large-page collapse\n\nLoading and unloading modules concurrently on several CPUs on a KASAN\nbuild, with a short delay injected at the CPA page-table lookup to\nwiden the window, faults within minutes:\n\n  BUG: KASAN: use-after-free in __change_page_attr+0x7cc/0x7e0\n  Write of size 8 at addr ffff888181139718 by task modprobe\n  ...\n  The buggy address belongs to the physical page:\n   pfn:0x181139 ... page_type: f2(table)\n\ncpa_collapse_large_pages() rebuilds a leaf PMD from its 4K PTEs and\nfrees the old PTE-table pages, while __change_page_attr() fetches a\nPTE pointer from a lockless lookup_address_in_pgd_attr() and writes\nit with set_pte_atomic() only later. When module text is served from\na shared large ROX mapping the two run on the same PMD:\n\n  CPU A (module load)              CPU B (module finalize)\n  -------------------              -----------------------\n  execmem_make_temp_rw\n   set_memory_nx\n    __change_page_attr\n     split 2M -> 4K table P\n     kpte = &P[i]  (lockless)\n                                   execmem_restore_rox\n                                    set_memory_rox (CPA_COLLAPSE)\n                                     cpa_collapse_large_pages\n                                      rebuild leaf PMD\n                                      flush_tlb_all\n                                      pagetable_free(P)\n     set_pte_atomic(kpte, ...)\n       -> writes into freed P\n\nP is a page-table page (page_type: table), reused at once, so the\nwrite corrupts whatever got the page next: a bad-pte or bad-page\nsplat, or a fatal fault once P has been turned into read-only text.\n\nThe flush_tlb_all() before the free does not close this: its IPI only\nserializes against page-table walkers that run with interrupts off\n(e.g. GUP-fast); the walk in __change_page_attr() runs with interrupts\non, so nothing stops it from holding a stale pointer into P.\n\nSerialize the collapse - the PMD rebuild, TLB flush and PTE-table\nfree - under cpa_lock, the same lock __change_page_attr() now takes\nunconditionally since commit (\"x86/mm/pat: stop gating cpa_lock on\ndebug_pagealloc_enabled()\"), so a concurrent walker can no longer\nhold a pointer into a table the collapse is about to free.","state":0,"publishedAt":"2026-09-17T16:10:51.612+00:00","modifiedAt":"2026-10-19T09:05:02.188+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/pat/set_memory.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"41d88484c71cd4f659348da41b7b5b3dbd3be1f6\",\n                            \"lessThan\": \"591b6fac9df3f43522e8ff6eed8662f8b6f1a124\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"41d88484c71cd4f659348da41b7b5b3dbd3be1f6\",\n                            \"lessThan\": \"fb97d1d6c20692e15247fa5c8b894b2325e38aee\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"41d88484c71cd4f659348da41b7b5b3dbd3be1f6\",\n                            \"lessThan\": \"1aac65f3e651334259ecb2a5f5ddb81c01f02599\",\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\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"arch/x86/mm/pat/set_memory.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.15\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.15\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.52\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.6\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/591b6fac9df3f43522e8ff6eed8662f8b6f1a124","https://git.kernel.org/stable/c/fb97d1d6c20692e15247fa5c8b894b2325e38aee","https://git.kernel.org/stable/c/1aac65f3e651334259ecb2a5f5ddb81c01f02599"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-93066","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-93066","identifiers":["CVE-2026-93066"]},"retained":false,"historicalAffected":[]}],"coverage":[]}