From c8263bd605009355edf781f2dd711de633998475 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Wed, 2 Mar 2022 17:35:30 -0800 Subject: mm/munlock: mlock_vma_page() check against VM_SPECIAL Although mmap_region() and mlock_fixup() take care that VM_LOCKED is never left set on a VM_SPECIAL vma, there is an interval while file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may still be set while VM_SPECIAL bits are added: so mlock_vma_page() should ignore VM_LOCKED while any VM_SPECIAL bits are set. This showed up as a "Bad page" still mlocked, when vfree()ing pages which had been vm_inserted by remap_vmalloc_range_partial(): while release_pages() and __page_cache_release(), and so put_page(), catch pages still mlocked when freeing (and clear_page_mlock() caught them when unmapping), the vfree() path is unprepared for them: fix it? but these pages should not have been mlocked in the first place. I assume that an mlockall(MCL_FUTURE) had been done in the past; or maybe the user got to specify MAP_LOCKED on a vmalloc'ing driver mmap. Signed-off-by: Hugh Dickins Signed-off-by: Matthew Wilcox (Oracle) --- mm/internal.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'mm/internal.h') diff --git a/mm/internal.h b/mm/internal.h index 18af980bb1b8..450a2c8a43f3 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -413,8 +413,15 @@ void mlock_page(struct page *page); static inline void mlock_vma_page(struct page *page, struct vm_area_struct *vma, bool compound) { - /* VM_IO check prevents migration from double-counting during mlock */ - if (unlikely((vma->vm_flags & (VM_LOCKED|VM_IO)) == VM_LOCKED) && + /* + * The VM_SPECIAL check here serves two purposes. + * 1) VM_IO check prevents migration from double-counting during mlock. + * 2) Although mmap_region() and mlock_fixup() take care that VM_LOCKED + * is never left set on a VM_SPECIAL vma, there is an interval while + * file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may + * still be set while VM_SPECIAL bits are added: so ignore it then. + */ + if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED) && (compound || !PageTransCompound(page))) mlock_page(page); } -- cgit v1.2.3