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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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