[RFC PATCH 2/3] integrity: use call_read_iter to calculate the file hash

[Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>]

This patch replaces the ->read file operation method in
integrity_kernel_read() with the newer ->read_iter and sets the
read_iter rwf flag to indicate that the i_rwsem has been taken
exclusively.

Signed-off-by:  Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
---
 security/integrity/iint.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index c84e05866052..df406bb96792 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -16,11 +16,13 @@
  *	  using a rbtree tree.
  */
 #include <linux/slab.h>
+#include <linux/fs.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/rbtree.h>
 #include <linux/file.h>
 #include <linux/uaccess.h>
+#include <linux/uio.h>
 #include "integrity.h"
 
 static struct rb_root integrity_iint_tree = RB_ROOT;
@@ -184,18 +186,25 @@ security_initcall(integrity_iintcache_init);
 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;
+	struct inode *inode = file_inode(file);
+	struct kvec iov = { .iov_base = addr, .iov_len = count };
+	struct kiocb kiocb;
+	struct iov_iter iter;
 	ssize_t ret;
 
+	lockdep_assert_held(&inode->i_rwsem);
+
 	if (!(file->f_mode & FMODE_READ))
 		return -EBADF;
+	if (!file->f_op->read_iter)
+		return -EBADF;
 
-	old_fs = get_fs();
-	set_fs(get_ds());
-	ret = __vfs_read(file, buf, count, &offset);
-	set_fs(old_fs);
+	init_sync_kiocb(&kiocb, file);
+	kiocb.ki_pos = offset;
+	iov_iter_kvec(&iter, READ | ITER_KVEC, &iov, 1, count);
 
+	ret = call_read_iter(file, &kiocb, &iter, 1);
+	BUG_ON(ret == -EIOCBQUEUED);
 	return ret;
 }
 
-- 
2.7.4