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X-Stat-Signature: p8mxxwbasjdnyrp9q684iru69mhpjwce X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 23D42140005 X-HE-Tag: 1772522754-375232 X-HE-Meta: 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 7Wc3UUKn JbuNHOXkQKvWueJCbuYyr630C8wjxSim2JsdOhPclo7kzNrLm+KsIL+bpL0rVF87WMKpy+EIlvnt0HOrDgziIdqqCgA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 02, 2026 at 12:50:32PM -0800, Andrew Morton wrote: > On Mon, 2 Mar 2026 17:19:15 +0000 Lorenzo Stoakes wrote: > > > On Mon, Mar 02, 2026 at 06:10:06PM +0100, David Hildenbrand (Arm) wrote: > > > There are already patches in flight: > > > > > > https://lore.kernel.org/r/aaBVaHs8rIkNcwM0@chrisdown.name > > > > Yup, if people would actually cc the right people I'd not have wasted my > > afternoon. > > > > Replying there. > > > > I'm not sure where this is headed but I'll queue this patch for now, to > get it some testing, to lessen duplicated bug reports and to generally track things. Hi Andrew - We should drop my patch and take Chris's. However, life isn't so simple :) as there's been some confusion with his series since his email client seemed to mess up somehow and a couple patches need to be squashed on one another. So to make life easier, I enclose a squashed patch (combining the commit message from both), with my R-b, T-b tags attached, please replace my patch with this one. Also, could you make this into a 2 patch series with https://lore.kernel.org/linux-mm/aaBWG4fajXXbjpVN@chrisdown.name/ _after_ this one? mm-unstable (I'm not sure why we're rushing changes there so quick...) had _only_ this regression test patch in it, so we were left with a kernel that splatted on running mm selftests, which is not what we want. (It seems to me this is what mm-new is for, and it seems we have some holes in our testing still since this got thorugh). Please drop the patch you have for this already in mm-unstable and make sure we only have it _after_ the fix is applied :) Thanks, Lorenzo ----8<---- >From fbabbc38c000308d2c621a4b3ec1f4bca1d71c1d Mon Sep 17 00:00:00 2001 From: Chris Down Date: Tue, 3 Mar 2026 07:21:21 +0000 Subject: [PATCH] mm/huge_memory: Fix use of NULL folio in move_pages_huge_pmd() move_pages_huge_pmd() handles UFFDIO_MOVE for both normal THPs and huge zero pages. For the huge zero page path, src_folio is explicitly set to NULL, and is used as a sentinel to skip folio operations like lock and rmap. In the huge zero page branch, src_folio is NULL, so folio_mk_pmd(NULL, pgprot) passes NULL through folio_pfn() and page_to_pfn(). With SPARSEMEM_VMEMMAP this silently produces a bogus PFN, installing a PMD pointing to non-existent physical memory. On other memory models it is a NULL dereference. Use page_folio(src_page) to obtain the valid huge zero folio from the page, which was obtained from pmd_page() and remains valid throughout. After commit d82d09e48219 ("mm/huge_memory: mark PMD mappings of the huge zero folio special"), moved huge zero PMDs must remain special so vm_normal_page_pmd() continues to treat them as special mappings. move_pages_huge_pmd() currently reconstructs the destination PMD in the huge zero page branch, which drops PMD state such as pmd_special() on architectures with CONFIG_ARCH_HAS_PTE_SPECIAL. As a result, vm_normal_page_pmd() can treat the moved huge zero PMD as a normal page and corrupt its refcount. Instead of reconstructing the PMD from the folio, derive the destination entry from src_pmdval after pmdp_huge_clear_flush(), then handle the PMD metadata the same way move_huge_pmd() does for moved entries by marking it soft-dirty and clearing uffd-wp. Fixes: e3981db444a0 ("mm: add folio_mk_pmd()") Cc: stable@vger.kernel.org Reviewed-by: Lorenzo Stoakes Tested-by: Lorenzo Stoakes Signed-off-by: Chris Down --- mm/huge_memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8e2746ea74ad..c5d3e7bf6414 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2797,7 +2797,8 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma); } else { src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); - _dst_pmd = folio_mk_pmd(src_folio, dst_vma->vm_page_prot); + _dst_pmd = move_soft_dirty_pmd(src_pmdval); + _dst_pmd = clear_uffd_wp_pmd(_dst_pmd); } set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd); -- 2.53.0