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authorYang Shi <shy828301@gmail.com>2021-10-28 14:36:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-10-28 17:18:55 -0700
commita4aeaa06d45e90f9b279f0b09de84bd00006e733 (patch)
tree4c520713adb8533a463e899239c931b484e4422f /mm/khugepaged.c
parent74c42e1baacf206338b1dd6b6199ac964512b5bb (diff)
downloadlwn-a4aeaa06d45e90f9b279f0b09de84bd00006e733.tar.gz
lwn-a4aeaa06d45e90f9b279f0b09de84bd00006e733.zip
mm: khugepaged: skip huge page collapse for special files
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@gmail.com: fix vm_file check [3]] Link: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ [1] Link: https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@google.com/ [2] Link: https://lkml.kernel.org/r/CAHbLzkqTW9U3VvTu1Ki5v_cLRC9gHW+znBukg_ycergE0JWj-A@mail.gmail.com [3] Link: https://lkml.kernel.org/r/20211027195221.3825-1-shy828301@gmail.com Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Yang Shi <shy828301@gmail.com> Reported-by: Hao Sun <sunhao.th@gmail.com> Reported-by: syzbot+aae069be1de40fb11825@syzkaller.appspotmail.com Cc: Matthew Wilcox <willy@infradead.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Song Liu <songliubraving@fb.com> Cc: Andrea Righi <andrea.righi@canonical.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/khugepaged.c')
-rw-r--r--mm/khugepaged.c19
1 files changed, 11 insertions, 8 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 48de4e1b0783..8a8b3aa92937 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -445,22 +445,25 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
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 &&
- !inode_is_open_for_write(vma->vm_file->f_inode) &&
(vm_flags & VM_EXEC)) {
- return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
- HPAGE_PMD_NR);
+ struct inode *inode = vma->vm_file->f_inode;
+
+ return !inode_is_open_for_write(inode) &&
+ S_ISREG(inode->i_mode);
}
if (!vma->anon_vma || vma->vm_ops)