smb3: missing inode locks in zero range

smb3 fallocate zero range was not grabbing the inode or filemap_invalidate
locks so could have race with pagemap reinstantiating the page.

Cc: stable@vger.kernel.org
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2ops.c

@@ -3307,26 +3307,43 @@ get_smb2_acl(struct cifs_sb_info *cifs_sb,
 	return pntsd;
 }
 
+static long smb3_zero_data(struct file *file, struct cifs_tcon *tcon,
+			     loff_t offset, loff_t len, unsigned int xid)
+{
+	struct cifsFileInfo *cfile = file->private_data;
+	struct file_zero_data_information fsctl_buf;
+
+	cifs_dbg(FYI, "Offset %lld len %lld\n", offset, len);
+
+	fsctl_buf.FileOffset = cpu_to_le64(offset);
+	fsctl_buf.BeyondFinalZero = cpu_to_le64(offset + len);
+
+	return SMB2_ioctl(xid, tcon, cfile->fid.persistent_fid,
+			  cfile->fid.volatile_fid, FSCTL_SET_ZERO_DATA,
+			  (char *)&fsctl_buf,
+			  sizeof(struct file_zero_data_information),
+			  0, NULL, NULL);
+}
+
 static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 			    loff_t offset, loff_t len, bool keep_size)
 {
 	struct cifs_ses *ses = tcon->ses;
-	struct inode *inode;
-	struct cifsInodeInfo *cifsi;
+	struct inode *inode = file_inode(file);
+	struct cifsInodeInfo *cifsi = CIFS_I(inode);
 	struct cifsFileInfo *cfile = file->private_data;
-	struct file_zero_data_information fsctl_buf;
 	long rc;
 	unsigned int xid;
 	__le64 eof;
 
 	xid = get_xid();
 
-	inode = d_inode(cfile->dentry);
-	cifsi = CIFS_I(inode);
-
 	trace_smb3_zero_enter(xid, cfile->fid.persistent_fid, tcon->tid,
 			      ses->Suid, offset, len);
 
+	inode_lock(inode);
+	filemap_invalidate_lock(inode->i_mapping);
+
 	/*
 	 * We zero the range through ioctl, so we need remove the page caches
 	 * first, otherwise the data may be inconsistent with the server.
@@ -3334,26 +3351,12 @@ static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 	truncate_pagecache_range(inode, offset, offset + len - 1);
 
 	/* if file not oplocked can't be sure whether asking to extend size */
-	if (!CIFS_CACHE_READ(cifsi))
-		if (keep_size == false) {
-			rc = -EOPNOTSUPP;
-			trace_smb3_zero_err(xid, cfile->fid.persistent_fid,
-				tcon->tid, ses->Suid, offset, len, rc);
-			free_xid(xid);
-			return rc;
-		}
-
-	cifs_dbg(FYI, "Offset %lld len %lld\n", offset, len);
-
-	fsctl_buf.FileOffset = cpu_to_le64(offset);
-	fsctl_buf.BeyondFinalZero = cpu_to_le64(offset + len);
+	rc = -EOPNOTSUPP;
+	if (keep_size == false && !CIFS_CACHE_READ(cifsi))
+		goto zero_range_exit;
 
-	rc = SMB2_ioctl(xid, tcon, cfile->fid.persistent_fid,
-			cfile->fid.volatile_fid, FSCTL_SET_ZERO_DATA,
-			(char *)&fsctl_buf,
-			sizeof(struct file_zero_data_information),
-			0, NULL, NULL);
-	if (rc)
+	rc = smb3_zero_data(file, tcon, offset, len, xid);
+	if (rc < 0)
 		goto zero_range_exit;
 
 	/*
@@ -3366,6 +3369,8 @@ static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 	}
 
  zero_range_exit:
+	filemap_invalidate_unlock(inode->i_mapping);
+	inode_unlock(inode);
 	free_xid(xid);
 	if (rc)
 		trace_smb3_zero_err(xid, cfile->fid.persistent_fid, tcon->tid,