integrity/ima: switch to using __kernel_read

__kernel_read has a bunch of additional sanity checks, and this moves
the set_fs out of non-core code.
Signed-off-by: Christoph Hellwig <hch@lst.de>

security/integrity/iint.c

@@ -188,19 +188,7 @@ DEFINE_LSM(integrity) = {
 int integrity_kernel_read(struct file *file, loff_t offset,
 			  void *addr, unsigned long count)
 {
-	mm_segment_t old_fs;
-	char __user *buf = (char __user *)addr;
-	ssize_t ret;
-
-	if (!(file->f_mode & FMODE_READ))
-		return -EBADF;
-
-	old_fs = get_fs();
-	set_fs(KERNEL_DS);
-	ret = __vfs_read(file, buf, count, &offset);
-	set_fs(old_fs);
-
-	return ret;
+	return __kernel_read(file, addr, count, &offset);
 }
 
 /*