From dfb190302d2b4af86c6ae48af0d3b09f28b35460 Mon Sep 17 00:00:00 2001 From: Li Zhe Date: Thu, 22 Oct 2026 11:45:41 +0800 Subject: [PATCH] mm/hugetlb: fix mremap move length truncation Patch series "mm/hugetlb: fix mremap bugs", v3. This series fixes a few hugetlb mremap bugs. Patch 1 fixes the return type of move_hugetlb_page_tables(), so large hugetlb moves cannot be truncated when reported back to the generic mremap code. Patch 2 disables hugetlb PMD sharing for UFFD missing mode, so UFFDIO_POISON markers cannot become visible through shared PMD page tables. Patch 3 fixes the recursive i_mmap_rwsem deadlock in the hugetlb mremap path by avoiding the destination PMD sharing allocation path while the mapping lock is already held for write. This patch (of 3): move_hugetlb_page_tables() returns the number of bytes moved, but its return type is int while the generic move_page_tables() path uses unsigned long lengths. A hugetlb mremap() move length above INT_MAX can therefore be misreported to copy_vma_and_data(). The out-of-range conversion to int is implementation-defined; on common 64-bit builds, for example, a 4 GiB move can be reported as zero, making the caller treat the move as a failure and use the wrong length for rollback. Return unsigned long from move_hugetlb_page_tables(), matching move_page_tables() and preserving the full byte count. Link: https://lore.kernel.org/20261022034543.51226-1-lizhe.67@bytedance.com Link: https://lore.kernel.org/20261022034543.51226-2-lizhe.67@bytedance.com Fixes: 550a7d60bd5e ("mm, hugepages: add mremap() support for hugepage backed vma") Signed-off-by: Li Zhe Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Cc: Muchun Song Cc: Oscar Salvador Cc: Peter Xu Cc: Mike Rapoport Cc: Jose A. Perez de Azpillaga Cc: --- include/linux/hugetlb.h | 15 ++++++--------- mm/hugetlb.c | 7 +++---- 2 files changed, 9 insertions(+), 13 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 5029c7241863..58f755e70e96 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -121,10 +121,9 @@ void hugepage_put_subpool(struct hugepage_subpool *spool); void hugetlb_dup_vma_private(struct vm_area_struct *vma); void clear_vma_resv_huge_pages(struct vm_area_struct *vma); -int move_hugetlb_page_tables(struct vm_area_struct *vma, - struct vm_area_struct *new_vma, - unsigned long old_addr, unsigned long new_addr, - unsigned long len); +unsigned long move_hugetlb_page_tables(struct vm_area_struct *vma, + struct vm_area_struct *new_vma, unsigned long old_addr, + unsigned long new_addr, unsigned long len); int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *, struct vm_area_struct *); void unmap_hugepage_range(struct vm_area_struct *, @@ -338,11 +337,9 @@ static inline int copy_hugetlb_page_range(struct mm_struct *dst, return 0; } -static inline int move_hugetlb_page_tables(struct vm_area_struct *vma, - struct vm_area_struct *new_vma, - unsigned long old_addr, - unsigned long new_addr, - unsigned long len) +static inline unsigned long move_hugetlb_page_tables(struct vm_area_struct *vma, + struct vm_area_struct *new_vma, unsigned long old_addr, + unsigned long new_addr, unsigned long len) { BUG(); return 0; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index da5d04edf7c1..506729ebaee7 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5195,10 +5195,9 @@ static void move_huge_pte(struct vm_area_struct *vma, unsigned long old_addr, spin_unlock(dst_ptl); } -int move_hugetlb_page_tables(struct vm_area_struct *vma, - struct vm_area_struct *new_vma, - unsigned long old_addr, unsigned long new_addr, - unsigned long len) +unsigned long move_hugetlb_page_tables(struct vm_area_struct *vma, + struct vm_area_struct *new_vma, unsigned long old_addr, + unsigned long new_addr, unsigned long len) { struct hstate *h = hstate_vma(vma); struct address_space *mapping = vma->vm_file->f_mapping;