xfs: prevent swapext from operating on write-only files
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@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
index 5bba29a..7f159d2 100644
--- a/fs/xfs/xfs_dfrag.c
+++ b/fs/xfs/xfs_dfrag.c
@@ -69,7 +69,9 @@
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 @@
}
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;