From 68589bc353037f233fe510ad9ff432338c95db66 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 14 Nov 2006 02:03:32 -0800 Subject: [PATCH] hugetlb: prepare_hugepage_range check offset too (David:) If hugetlbfs_file_mmap() returns a failure to do_mmap_pgoff() - for example, because the given file offset is not hugepage aligned - then do_mmap_pgoff will go to the unmap_and_free_vma backout path. But at this stage the vma hasn't been marked as hugepage, and the backout path will call unmap_region() on it. That will eventually call down to the non-hugepage version of unmap_page_range(). On ppc64, at least, that will cause serious problems if there are any existing hugepage pagetable entries in the vicinity - for example if there are any other hugepage mappings under the same PUD. unmap_page_range() will trigger a bad_pud() on the hugepage pud entries. I suspect this will also cause bad problems on ia64, though I don't have a machine to test it on. (Hugh:) prepare_hugepage_range() should check file offset alignment when it checks virtual address and length, to stop MAP_FIXED with a bad huge offset from unmapping before it fails further down. PowerPC should apply the same prepare_hugepage_range alignment checks as ia64 and all the others do. Then none of the alignment checks in hugetlbfs_file_mmap are required (nor is the check for too small a mapping); but even so, move up setting of VM_HUGETLB and add a comment to warn of what David Gibson discovered - if hugetlbfs_file_mmap fails before setting it, do_mmap_pgoff's unmap_region when unwinding from error will go the non-huge way, which may cause bad behaviour on architectures (powerpc and ia64) which segregate their huge mappings into a separate region of the address space. Signed-off-by: Hugh Dickins Cc: "Luck, Tony" Cc: "David S. Miller" Acked-by: Adam Litke Acked-by: David Gibson Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/hugetlbfs/inode.c | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-) (limited to 'fs/hugetlbfs') diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 0bea6a6..7f47569 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -62,24 +62,19 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) loff_t len, vma_len; int ret; - if (vma->vm_pgoff & (HPAGE_SIZE / PAGE_SIZE - 1)) - return -EINVAL; - - if (vma->vm_start & ~HPAGE_MASK) - return -EINVAL; - - if (vma->vm_end & ~HPAGE_MASK) - return -EINVAL; - - if (vma->vm_end - vma->vm_start < HPAGE_SIZE) - return -EINVAL; + /* + * vma alignment has already been checked by prepare_hugepage_range. + * If you add any error returns here, do so after setting VM_HUGETLB, + * so is_vm_hugetlb_page tests below unmap_region go the right way + * when do_mmap_pgoff unwinds (may be important on powerpc and ia64). + */ + vma->vm_flags |= VM_HUGETLB | VM_RESERVED; + vma->vm_ops = &hugetlb_vm_ops; vma_len = (loff_t)(vma->vm_end - vma->vm_start); mutex_lock(&inode->i_mutex); file_accessed(file); - vma->vm_flags |= VM_HUGETLB | VM_RESERVED; - vma->vm_ops = &hugetlb_vm_ops; ret = -ENOMEM; len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); -- cgit v1.1