splice: Apply generic position and size checks to each write

commit 894c6350 from the 3.2-stable branch.

We need to check the position and size of file writes against various
limits, using generic_write_check().  This was not being done for
the splice write path.  It was fixed upstream by commit 8d020765
("->splice_write() via ->write_iter()") but we can't apply that.

CVE-2014-7822
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[Ben fixed it in 3.2 stable, i ported it to 3.10 stable]
Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ocfs2/file.c

@@ -2459,12 +2459,14 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
 	struct address_space *mapping = out->f_mapping;
 	struct inode *inode = mapping->host;
 	struct splice_desc sd = {
-		.total_len = len,
 		.flags = flags,
-		.pos = *ppos,
 		.u.file = out,
 	};
-
+	ret = generic_write_checks(out, ppos, &len, 0);
+	if(ret)
+		return ret;
+	sd.total_len = len;
+	sd.pos = *ppos;
 
 	trace_ocfs2_file_splice_write(inode, out, out->f_path.dentry,
 			(unsigned long long)OCFS2_I(inode)->ip_blkno,

fs/splice.c

@@ -1012,13 +1012,17 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 	struct address_space *mapping = out->f_mapping;
 	struct inode *inode = mapping->host;
 	struct splice_desc sd = {
-		.total_len = len,
 		.flags = flags,
-		.pos = *ppos,
 		.u.file = out,
 	};
 	ssize_t ret;
 
+	ret = generic_write_checks(out, ppos, &len, S_ISBLK(inode->i_mode));
+	if (ret)
+		return ret;
+	sd.total_len = len;
+	sd.pos = *ppos;
+
 	pipe_lock(pipe);
 
 	splice_from_pipe_begin(&sd);