This is a note to let you know that I've just added the patch titled mm: khugepaged: skip huge page collapse for special files to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-khugepaged-skip-huge-page-collapse-for-special-files.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From a4aeaa06d45e90f9b279f0b09de84bd00006e733 Mon Sep 17 00:00:00 2001 From: Yang Shi <shy828301@xxxxxxxxx> Date: Thu, 28 Oct 2021 14:36:30 -0700 Subject: mm: khugepaged: skip huge page collapse for special files From: Yang Shi <shy828301@xxxxxxxxx> commit a4aeaa06d45e90f9b279f0b09de84bd00006e733 upstream. The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [shy828301@xxxxxxxxx: fix vm_file check [3]] Link: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@xxxxxxxxxxxxxx/ [1] Link: https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@xxxxxxxxxx/ [2] Link: https://lkml.kernel.org/r/CAHbLzkqTW9U3VvTu1Ki5v_cLRC9gHW+znBukg_ycergE0JWj-A@xxxxxxxxxxxxxx [3] Link: https://lkml.kernel.org/r/20211027195221.3825-1-shy828301@xxxxxxxxx Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx> Reported-by: Hao Sun <sunhao.th@xxxxxxxxx> Reported-by: syzbot+aae069be1de40fb11825@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Song Liu <songliubraving@xxxxxx> Cc: Andrea Righi <andrea.righi@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/khugepaged.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -443,21 +443,24 @@ static bool hugepage_vma_check(struct vm if (!transhuge_vma_enabled(vma, vm_flags)) return false; + if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - + vma->vm_pgoff, HPAGE_PMD_NR)) + return false; + /* Enabled via shmem mount options or sysfs settings. */ - if (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) { - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); - } + if (shmem_file(vma->vm_file)) + return shmem_huge_enabled(vma); /* THP settings require madvise. */ if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) return false; - /* Read-only file mappings need to be aligned for THP to work. */ + /* Only regular file is valid */ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && (vm_flags & VM_DENYWRITE)) { - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); + struct inode *inode = vma->vm_file->f_inode; + + return S_ISREG(inode->i_mode); } if (!vma->anon_vma || vma->vm_ops) Patches currently in stable-queue which might be from shy828301@xxxxxxxxx are queue-5.10/mm-khugepaged-skip-huge-page-collapse-for-special-files.patch queue-5.10/mm-filemap-check-if-thp-has-hwpoisoned-subpage-for-pmd-page-fault.patch queue-5.10/mm-hwpoison-remove-the-unnecessary-thp-check.patch