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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93720493f35sm609512385a.9.2026.08.21.07.50.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2026 07:50:08 -0700 (PDT) From: Gregory Price To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org, david@kernel.org, vbabka@kernel.org, jannh@google.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, peterx@redhat.com, jgg@ziepe.ca, sashiko-bot , stable@vger.kernel.org Subject: [PATCH 2/2] mm/madvise: use vm_normal_folio_pmd() in cold/pageout PMD range Date: Fri, 21 Aug 2026 10:49:47 -0400 Message-ID: <20260821144947.167382-3-gourry@gourry.net> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260821144947.167382-1-gourry@gourry.net> References: <20260821144947.167382-1-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit mmap a VM_MIXEDMAP region whose ->huge_fault installs a PMD through vmf_insert_pfn_pmd() - mshv_vtl_low does this, and needs CAP_SYS_ADMIN to open - then madvise(p, PMD_SIZE, MADV_PAGEOUT); With a stand-in module for the driver: BUG: unable to handle page fault for address: fffff587c0000008 RIP: 0010:madvise_cold_or_pageout_pte_range+0x410/0x9b0 walk_pgd_range+0x52b/0xaf0 __walk_page_range+0x6a/0x1d0 walk_page_range_vma_unsafe+0x8e/0x120 madvise_pageout+0xb2/0x180 madvise_vma_behavior+0x46b/0xa90 do_madvise+0x108/0x190 __x64_sys_madvise+0x26/0x30 Nothing validates the pfn on the way in: can_madv_lru_vma() rejects VM_PFNMAP, but not VM_MIXEDMAP can_fault() *pfn = vmf->pgoff & ~(mask >> PAGE_SHIFT); vmf_insert_pfn_pmd() no pfn_valid() check pmd_folio() pfn_to_page() -> unpopulated vmemmap Even with a valid pfn the path is wrong. The mapping carries no rmap, so folio_maybe_mapped_shared() sees mapcount 0, and the walker goes on to folio_deactivate(), or folio_isolate_lru() plus reclaim_pages(), against a folio this mapping does not own. Use vm_normal_folio_pmd() and skip on NULL, as the PTE half of this same walker already does with vm_normal_folio(). The huge zero PMD is already handled further up by is_huge_zero_pmd(). Fixes: 3c8e44c9b369 ("mm: mark special bits for huge pfn mappings when inject") Reported-by: sashiko-bot Closes: https://sashiko.dev/#/patchset/20260817220810.1175596-1-gourry%40gourry.net Cc: # v6.19+ Assisted-by: Claude:claude-opus-5 Signed-off-by: Gregory Price (Meta) --- mm/madvise.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index ffd6a68320a8..ab362bc482a5 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -393,7 +393,9 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, goto huge_unlock; } - folio = pmd_folio(orig_pmd); + folio = vm_normal_folio_pmd(vma, addr, orig_pmd); + if (!folio) + goto huge_unlock; if (folio_is_zone_device(folio)) goto huge_unlock; -- 2.55.0