fs: remove the access_ok() check in ioctl_fiemap

access_ok just checks we are fed a proper user pointer.  We also do that
in copy_to_user itself, so no need to do this early.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Link: https://lore.kernel.org/r/20200523073016.2944131-9-hch@lst.deSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ioctl.c

@@ -213,13 +213,9 @@ static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
 	fieinfo.fi_extents_max = fiemap.fm_extent_count;
 	fieinfo.fi_extents_start = ufiemap->fm_extents;
 
-	if (fiemap.fm_extent_count != 0 &&
-	    !access_ok(fieinfo.fi_extents_start,
-		       fieinfo.fi_extents_max * sizeof(struct fiemap_extent)))
-		return -EFAULT;
-
 	error = inode->i_op->fiemap(inode, &fieinfo, fiemap.fm_start,
 			fiemap.fm_length);
+
 	fiemap.fm_flags = fieinfo.fi_flags;
 	fiemap.fm_mapped_extents = fieinfo.fi_extents_mapped;
 	if (copy_to_user(ufiemap, &fiemap, sizeof(fiemap)))