On 2017/12/5 13:24, Matthew Wilcox Wrote:
> On Tue, Dec 05, 2017 at 11:32:10AM +0800, zhangyi (F) wrote:
>> On 32bit machine, when mmap2 a large enough file with pgoff more than
>> ULONG_MAX >> PAGE_SHIFT, it will trigger offset overflow and lead to
>> unmap the wrong page in dax_insert_mapping_entry(). This patch cast
>> pgoff to 64bit to prevent the overflow.
>
> You're quite correct, and you've solved this problem the same way as the
> other half-dozen users in the kernel with the problem, so good job.
>
> I think we can do better though. How does this look?
Yes, It looks better to me. I notice that unmap_mapping_range() have
an empty instance in nommu.c for the no mmu machine, do we need another
unmap_mapping_pages() too ? Not test it.
Thanks,
Yi.
>>From 9f8f30197eba970c82eea909624299c86b2c5f7e Mon Sep 17 00:00:00 2001
> From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> Date: Tue, 5 Dec 2017 00:15:54 -0500
> Subject: [PATCH] mm: Add unmap_mapping_pages
>
> Several users of unmap_mapping_range() would much prefer to express
> their range in pages rather than bytes. This leads to four places
> in the current tree where there are bugs on 32-bit kernels because of
> missing casts.
>
> Conveniently, unmap_mapping_range() actually converts from bytes into
> pages, so hoist the guts of unmap_mapping_range() into a new function
> unmap_mapping_pages() and convert the callers.
>
> Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> Reported-by: "zhangyi (F)" <yi.zhang@xxxxxxxxxx>
> ---
> fs/dax.c | 19 ++++++-------------
> include/linux/mm.h | 2 ++
> mm/khugepaged.c | 3 +--
> mm/memory.c | 41 +++++++++++++++++++++++++++++------------
> mm/truncate.c | 23 +++++++----------------
> 5 files changed, 45 insertions(+), 43 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 95981591977a..6dd481f8216c 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -44,6 +44,7 @@
>
> /* The 'colour' (ie low bits) within a PMD of a page offset. */
> #define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
> +#define PG_PMD_NR (PMD_SIZE >> PAGE_SHIFT)
>
> static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
>
> @@ -375,8 +376,8 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
> * unmapped.
> */
> if (pmd_downgrade && dax_is_zero_entry(entry))
> - unmap_mapping_range(mapping,
> - (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
> + unmap_mapping_pages(mapping, index & ~PG_PMD_COLOUR,
> + PG_PMD_NR, 0);
>
> err = radix_tree_preload(
> mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
> @@ -538,12 +539,10 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
> if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_ZERO_PAGE)) {
> /* we are replacing a zero page with block mapping */
> if (dax_is_pmd_entry(entry))
> - unmap_mapping_range(mapping,
> - (vmf->pgoff << PAGE_SHIFT) & PMD_MASK,
> - PMD_SIZE, 0);
> + unmap_mapping_pages(mapping, vmf->pgoff & PG_PMD_COLOUR,
> + PG_PMD_NR, 0);
> else /* pte entry */
> - unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
> - PAGE_SIZE, 0);
> + unmap_mapping_pages(mapping, vmf->pgoff, 1, 0);
> }
>
> spin_lock_irq(&mapping->tree_lock);
> @@ -1269,12 +1268,6 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
> }
>
> #ifdef CONFIG_FS_DAX_PMD
> -/*
> - * The 'colour' (ie low bits) within a PMD of a page offset. This comes up
> - * more often than one might expect in the below functions.
> - */
> -#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
> -
> static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
> void *entry)
> {
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ee073146aaa7..0fa4b2d826fa 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1311,6 +1311,8 @@ void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
> unsigned long end, unsigned long floor, unsigned long ceiling);
> int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
> struct vm_area_struct *vma);
> +void unmap_mapping_pages(struct address_space *mapping,
> + pgoff_t start, pgoff_t nr, bool even_cows);
> void unmap_mapping_range(struct address_space *mapping,
> loff_t const holebegin, loff_t const holelen, int even_cows);
> int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index ea4ff259b671..431b4051b46c 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1399,8 +1399,7 @@ static void collapse_shmem(struct mm_struct *mm,
> }
>
> if (page_mapped(page))
> - unmap_mapping_range(mapping, index << PAGE_SHIFT,
> - PAGE_SIZE, 0);
> + unmap_mapping_pages(mapping, index, 1, 0);
>
> spin_lock_irq(&mapping->tree_lock);
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 85e7a87da79f..88aad8784421 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2791,9 +2791,36 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
> }
> }
>
> +/**
> + * unmap_mapping_pages() - Unmap pages from processes.
> + * @mapping: The address space containing pages to be unmapped.
> + * @start: Index of first page to be unmapped.
> + * @nr: Number of pages to be unmapped. 0 to unmap to end of file.
> + * @even_cows: Whether to unmap even private COWed pages.
> + *
> + * Unmap the pages in this address space from any userspace process which
> + * has them mmaped.
> + */
> +void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
> + pgoff_t nr, bool even_cows)
> +{
> + struct zap_details details = { };
> +
> + details.check_mapping = even_cows ? NULL : mapping;
> + details.first_index = start;
> + details.last_index = start + nr - 1;
> + if (details.last_index < details.first_index)
> + details.last_index = ULONG_MAX;
> +
> + i_mmap_lock_write(mapping);
> + if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
> + unmap_mapping_range_tree(&mapping->i_mmap, &details);
> + i_mmap_unlock_write(mapping);
> +}
> +
> /**
> * unmap_mapping_range - unmap the portion of all mmaps in the specified
> - * address_space corresponding to the specified page range in the underlying
> + * address_space corresponding to the specified byte range in the underlying
> * file.
> *
> * @mapping: the address space containing mmaps to be unmapped.
> @@ -2811,7 +2838,6 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
> void unmap_mapping_range(struct address_space *mapping,
> loff_t const holebegin, loff_t const holelen, int even_cows)
> {
> - struct zap_details details = { };
> pgoff_t hba = holebegin >> PAGE_SHIFT;
> pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
>
> @@ -2823,16 +2849,7 @@ void unmap_mapping_range(struct address_space *mapping,
> hlen = ULONG_MAX - hba + 1;
> }
>
> - details.check_mapping = even_cows ? NULL : mapping;
> - details.first_index = hba;
> - details.last_index = hba + hlen - 1;
> - if (details.last_index < details.first_index)
> - details.last_index = ULONG_MAX;
> -
> - i_mmap_lock_write(mapping);
> - if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
> - unmap_mapping_range_tree(&mapping->i_mmap, &details);
> - i_mmap_unlock_write(mapping);
> + unmap_mapping_pages(mapping, hba, hlen, even_cows);
> }
> EXPORT_SYMBOL(unmap_mapping_range);
>
> diff --git a/mm/truncate.c b/mm/truncate.c
> index e4b4cf0f4070..55dd8e1b1564 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -179,12 +179,8 @@ static void
> truncate_cleanup_page(struct address_space *mapping, struct page *page)
> {
> if (page_mapped(page)) {
> - loff_t holelen;
> -
> - holelen = PageTransHuge(page) ? HPAGE_PMD_SIZE : PAGE_SIZE;
> - unmap_mapping_range(mapping,
> - (loff_t)page->index << PAGE_SHIFT,
> - holelen, 0);
> + pgoff_t nr = PageTransHuge(page) ? HPAGE_PMD_NR : 1;
> + unmap_mapping_pages(mapping, page->index, nr, 0);
> }
>
> if (page_has_private(page))
> @@ -715,19 +711,15 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
> /*
> * Zap the rest of the file in one hit.
> */
> - unmap_mapping_range(mapping,
> - (loff_t)index << PAGE_SHIFT,
> - (loff_t)(1 + end - index)
> - << PAGE_SHIFT,
> - 0);
> + unmap_mapping_pages(mapping, index,
> + (1 + end - index), 0);
> did_range_unmap = 1;
> } else {
> /*
> * Just zap this page
> */
> - unmap_mapping_range(mapping,
> - (loff_t)index << PAGE_SHIFT,
> - PAGE_SIZE, 0);
> + unmap_mapping_pages(mapping, index,
> + 1, 0);
> }
> }
> BUG_ON(page_mapped(page));
> @@ -753,8 +745,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
> * get remapped later.
> */
> if (dax_mapping(mapping)) {
> - unmap_mapping_range(mapping, (loff_t)start << PAGE_SHIFT,
> - (loff_t)(end - start + 1) << PAGE_SHIFT, 0);
> + unmap_mapping_pages(mapping, start, end - start + 1, 0);
> }
> out:
> cleancache_invalidate_inode(mapping);
>
