From 3272cfc2525b3a2810a59312d7a1e6f04a0ca3ef Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Wed, 24 Feb 2021 12:07:54 -0800 Subject: hugetlb: fix copy_huge_page_from_user contig page struct assumption page structs are not guaranteed to be contiguous for gigantic pages. The routine copy_huge_page_from_user can encounter gigantic pages, yet it assumes page structs are contiguous when copying pages from user space. Since page structs for the target gigantic page are not contiguous, the data copied from user space could overwrite other pages not associated with the gigantic page and cause data corruption. Non-contiguous page structs are generally not an issue. However, they can exist with a specific kernel configuration and hotplug operations. For example: Configure the kernel with CONFIG_SPARSEMEM and !CONFIG_SPARSEMEM_VMEMMAP. Then, hotplug add memory for the area where the gigantic page will be allocated. Link: https://lkml.kernel.org/r/20210217184926.33567-2-mike.kravetz@oracle.com Fixes: 8fb5debc5fcd ("userfaultfd: hugetlbfs: add hugetlb_mcopy_atomic_pte for userfaultfd support") Signed-off-by: Mike Kravetz Cc: Zi Yan Cc: Davidlohr Bueso Cc: "Kirill A . Shutemov" Cc: Andrea Arcangeli Cc: Matthew Wilcox Cc: Oscar Salvador Cc: Joao Martins Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'mm/memory.c') diff --git a/mm/memory.c b/mm/memory.c index ef4e10c60b5f..784249f3307b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5177,17 +5177,19 @@ long copy_huge_page_from_user(struct page *dst_page, void *page_kaddr; unsigned long i, rc = 0; unsigned long ret_val = pages_per_huge_page * PAGE_SIZE; + struct page *subpage = dst_page; - for (i = 0; i < pages_per_huge_page; i++) { + for (i = 0; i < pages_per_huge_page; + i++, subpage = mem_map_next(subpage, dst_page, i)) { if (allow_pagefault) - page_kaddr = kmap(dst_page + i); + page_kaddr = kmap(subpage); else - page_kaddr = kmap_atomic(dst_page + i); + page_kaddr = kmap_atomic(subpage); rc = copy_from_user(page_kaddr, (const void __user *)(src + i * PAGE_SIZE), PAGE_SIZE); if (allow_pagefault) - kunmap(dst_page + i); + kunmap(subpage); else kunmap_atomic(page_kaddr); -- cgit