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    Subject[PATCH v2] hugetlbfs: fix bug in pgoff overflow checking
    Date
    This is a fix for a regression in 32 bit kernels caused by an
    invalid check for pgoff overflow in hugetlbfs mmap setup. The
    check incorrectly specified that the size of a loff_t was the
    same as the size of a long. The regression prevents mapping
    hugetlbfs files at offsets greater than 4GB on 32 bit kernels.

    On 32 bit kernels conversion from a page based unsigned long can
    not overflow a loff_t byte offset. Therefore, skip this check
    if sizeof(unsigned long) != sizeof(loff_t).

    Fixes: 63489f8e8211 ("hugetlbfs: check for pgoff value overflow")
    Cc: <stable@vger.kernel.org>
    Reported-by: Dan Rue <dan.rue@linaro.org>
    Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
    ---
    fs/hugetlbfs/inode.c | 10 +++++++---
    1 file changed, 7 insertions(+), 3 deletions(-)

    diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
    index b9a254dcc0e7..d508c7844681 100644
    --- a/fs/hugetlbfs/inode.c
    +++ b/fs/hugetlbfs/inode.c
    @@ -138,10 +138,14 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)

    /*
    * page based offset in vm_pgoff could be sufficiently large to
    - * overflow a (l)off_t when converted to byte offset.
    + * overflow a loff_t when converted to byte offset. This can
    + * only happen on architectures where sizeof(loff_t) ==
    + * sizeof(unsigned long). So, only check in those instances.
    */
    - if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
    - return -EINVAL;
    + if (sizeof(unsigned long) == sizeof(loff_t)) {
    + if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
    + return -EINVAL;
    + }

    /* must be huge page aligned */
    if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
    --
    2.13.6
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