cifs: revalidate mapping prior to satisfying read_iter request with cache=loose

Before satisfying a read with cache=loose, we should always check
that the pagecache is valid before allowing a read to be satisfied
out of it.

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 2c90d07c0b3a..888398067420 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -725,6 +725,19 @@ out_nls:
         goto out;
 }
 
+static ssize_t
+cifs_loose_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+        ssize_t rc;
+        struct inode *inode = file_inode(iocb->ki_filp);
+
+        rc = cifs_revalidate_mapping(inode);
+        if (rc)
+                return rc;
+
+        return generic_file_read_iter(iocb, iter);
+}
+
 static ssize_t cifs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
         struct inode *inode = file_inode(iocb->ki_filp);
@@ -881,7 +894,7 @@ const struct inode_operations cifs_symlink_inode_ops = {
 const struct file_operations cifs_file_ops = {
         .read = new_sync_read,
         .write = new_sync_write,
-        .read_iter = generic_file_read_iter,
+        .read_iter = cifs_loose_read_iter,
         .write_iter = cifs_file_write_iter,
         .open = cifs_open,
         .release = cifs_close,
@@ -939,7 +952,7 @@ const struct file_operations cifs_file_direct_ops = {
 const struct file_operations cifs_file_nobrl_ops = {
         .read = new_sync_read,
         .write = new_sync_write,
-        .read_iter = generic_file_read_iter,
+        .read_iter = cifs_loose_read_iter,
         .write_iter = cifs_file_write_iter,
         .open = cifs_open,
         .release = cifs_close,