{"id":"CVE-2026-72043","state":"PUBLISHED","title":"LoongArch: Fix missing dirty page tracking in {pte,pmd}_wrprotect()","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.","publishedAt":"2026-08-15T05:52:02.505Z","updatedAt":"2026-08-17T05:39:42.678Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"76f88650763a35cbf1384c65d66d096fa31cc58d","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"e8a916579e427af32f2de8213dfa23c5df6e6664","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"39bb21a4bff0d70058bf752d7b5aa2e2ccc864a9","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"a65f49b6f7ece756394f8f0e85570020e7fd0e35","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"e483da960892c41fa7f0cf0d2fc2410d65a483d6","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"018e9828eb523c638fa3d9bdf0fd4956b74555b2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/loongarch/include/asm/pgtable.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/loongarch/include/asm/pgtable.h"]}],"references":["https://git.kernel.org/stable/c/76f88650763a35cbf1384c65d66d096fa31cc58d","https://git.kernel.org/stable/c/e8a916579e427af32f2de8213dfa23c5df6e6664","https://git.kernel.org/stable/c/39bb21a4bff0d70058bf752d7b5aa2e2ccc864a9","https://git.kernel.org/stable/c/a65f49b6f7ece756394f8f0e85570020e7fd0e35","https://git.kernel.org/stable/c/e483da960892c41fa7f0cf0d2fc2410d65a483d6","https://git.kernel.org/stable/c/018e9828eb523c638fa3d9bdf0fd4956b74555b2"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72043.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72043","state":"PUBLISHED","datePublished":"2026-08-15T05:52:02.505Z","dateUpdated":"2026-08-17T05:39:42.678Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.902Z"},"containers":{"cna":{"title":"LoongArch: Fix missing dirty page tracking in {pte,pmd}_wrprotect()","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"76f88650763a35cbf1384c65d66d096fa31cc58d","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"e8a916579e427af32f2de8213dfa23c5df6e6664","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"39bb21a4bff0d70058bf752d7b5aa2e2ccc864a9","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"a65f49b6f7ece756394f8f0e85570020e7fd0e35","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"e483da960892c41fa7f0cf0d2fc2410d65a483d6","versionType":"git"},{"version":"09cfefb7fa70c3af011b0db0a513fd80b2f18abc","status":"affected","lessThan":"018e9828eb523c638fa3d9bdf0fd4956b74555b2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/loongarch/include/asm/pgtable.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/loongarch/include/asm/pgtable.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/76f88650763a35cbf1384c65d66d096fa31cc58d"},{"url":"https://git.kernel.org/stable/c/e8a916579e427af32f2de8213dfa23c5df6e6664"},{"url":"https://git.kernel.org/stable/c/39bb21a4bff0d70058bf752d7b5aa2e2ccc864a9"},{"url":"https://git.kernel.org/stable/c/a65f49b6f7ece756394f8f0e85570020e7fd0e35"},{"url":"https://git.kernel.org/stable/c/e483da960892c41fa7f0cf0d2fc2410d65a483d6"},{"url":"https://git.kernel.org/stable/c/018e9828eb523c638fa3d9bdf0fd4956b74555b2"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","baseScore":7.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is triggered via local syscalls (mmap/madvise/write/fork or clone) through dup_mmap()->copy_page_range()->pte_wrprotect() on LoongArch; it is not reachable from network-facing kernel services.\nAC:L - An unprivileged attacker can reliably reproduce the LTP madvise09 sequence (MADV_FREE, write, fork, then force reclaim) on LoongArch CPUs with hardware PTW; no races or victim-specific state beyond attacker-controlled memory pressure are required.\nPR:L - No special capabilities are needed; any local user can create private anonymous or file-backed COW mappings, write them, fork, and drive page reclaim using standard unprivileged syscalls.\nUI:N - Exploitation requires no action from another user; the attacker controls the full trigger sequence in their own process or in a service worker they operate.\nS:U - Impact is confined to kernel memory-management integrity on the host; it does not constitute a VM escape, sandbox escape, or IOMMU/DMA boundary bypass.\nC:H - Incorrectly treating hardware-dirty pages as clean during reclaim can free page frames without writeback or swap, leaving prior contents in the buddy allocator for reuse by other mappings and enabling cross-process information disclosure.\nI:H - Lost dirty tracking causes silent discard of modified pages during reclaim without writeback, corrupting private anonymous data and file-backed COW mappings when dirty pages are freed or swapped incorrectly.\nA:N - The defect causes silent data corruption rather than kernel oops, panic, or hang; the system remains operational even when pages are incorrectly reclaimed."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:39:42.678Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}