[179/205] xfs: prevent swapext from operating on write-only files

[Greg KH]

2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>

commit 1817176a86352f65210139d4c794ad2d19fc6b63 upstream.

This patch prevents user "foo" from using the SWAPEXT ioctl to swap
a write-only file owned by user "bar" into a file owned by "foo" and
subsequently reading it.  It does so by checking that the file
descriptors passed to the ioctl are also opened for reading.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/xfs/xfs_dfrag.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/xfs/xfs_dfrag.c
+++ b/fs/xfs/xfs_dfrag.c
@@ -69,7 +69,9 @@ xfs_swapext(
 		goto out;
 	}
 
-	if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND)) {
+	if (!(file->f_mode & FMODE_WRITE) ||
+	    !(file->f_mode & FMODE_READ) ||
+	    (file->f_flags & O_APPEND)) {
 		error = XFS_ERROR(EBADF);
 		goto out_put_file;
 	}
@@ -81,6 +83,7 @@ xfs_swapext(
 	}
 
 	if (!(tmp_file->f_mode & FMODE_WRITE) ||
+	    !(tmp_file->f_mode & FMODE_READ) ||
 	    (tmp_file->f_flags & O_APPEND)) {
 		error = XFS_ERROR(EBADF);
 		goto out_put_tmp_file;


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