{"cve":"CVE-2026-72043","nvd":{"published":"2026-08-15T06:21:13.480","modified":"2026-08-17T06:18:02.257","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nLoongArch: Fix missing dirty page tracking in {pte,pmd}_wrprotect()\n\nWhen hardware page table walker (PTW) is enabled on LoongArch, the CPU\nmay set _PAGE_DIRTY directly in the page table entry during a write TLB\nmiss, without going through the software TLB store handler. The software\nTLB store handler (tlbex.S:254) sets both _PAGE_DIRTY and_PAGE_MODIFIED\ntogether:\n\n    ori t0, t0, (_PAGE_VALID | _PAGE_DIRTY | _PAGE_MODIFIED)\n\nSince hardware PTW only sets _PAGE_DIRTY, the software-only bit, i.e.\n_PAGE_MODIFIED is left unchanged. This creates a window where a PTE has\n_PAGE_DIRTY set (hardware knows the page is dirty) but _PAGE_MODIFIED\nclear (software is unaware).\n\nWhen fork()/clone() triggers copy-on-write, __copy_present_ptes() calls\npte_wrprotect(), which unconditionally clears both the _PAGE_WRITE and\n_PAGE_DIRTY bits:\n\n    pte_val(pte) &= ~(_PAGE_WRITE | _PAGE_DIRTY);\n\nSince _PAGE_MODIFIED was never set, the dirtiness information is lost\ncompletely. Subsequently, when memory pressure triggers page reclaim,\npage_mkclean() / try_to_unmap() sees the page as clean (i.e. pte_dirty()\nreturns false) and the page may be freed without writeback, causing data\ncorruption.\n\nFix this by propagating the _PAGE_DIRTY bit to the _PAGE_MODIFIED bit in\nboth pte_wrprotect() and pmd_wrprotect() before clearing writeable bits:\n\n    if (pte_val(pte) & _PAGE_DIRTY)\n        pte_val(pte) |= _PAGE_MODIFIED;\n\nThe pmd_wrprotect() fix handles the CONFIG_TRANSPARENT_HUGEPAGE case,\nwhere pmd entries need the same treatment.\n\nThis ensures the software dirty tracking bit (checked by pte_dirty() and\npmd_dirty(), which read both the _PAGE_DIRTY and _PAGE_MODIFIED bits) is\npreserved across fork COW write-protection.\n\nThe issue was found by the LTP madvise09 test case, which exercises page\nreclaim after \"madvise(MADV_FREE), write and fork\" operation sequence on\nprivate anonymous mappings.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","score":7.1},"cwes":[],"references":["https://git.kernel.org/stable/c/018e9828eb523c638fa3d9bdf0fd4956b74555b2","https://git.kernel.org/stable/c/39bb21a4bff0d70058bf752d7b5aa2e2ccc864a9","https://git.kernel.org/stable/c/76f88650763a35cbf1384c65d66d096fa31cc58d","https://git.kernel.org/stable/c/a65f49b6f7ece756394f8f0e85570020e7fd0e35","https://git.kernel.org/stable/c/e483da960892c41fa7f0cf0d2fc2410d65a483d6"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:48:17.459049833+00:00"},"epss":{"cve":"CVE-2026-72043","score":0.00172,"percentile":0.0658,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}