[PATCH v3 08/13] vfs: copy_file_range needs to strip setuid bits and update timestamps

From: Amir Goldstein <amir73il@gmail.com>
To: "Darrick J . Wong" <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>,
	linux-xfs@vger.kernel.org,
	Olga Kornievskaia <olga.kornievskaia@gmail.com>,
	Luis Henriques <lhenriques@suse.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
	ceph-devel@vger.kernel.org, linux-nfs@vger.kernel.org,
	linux-cifs@vger.kernel.org
Subject: [PATCH v3 08/13] vfs: copy_file_range needs to strip setuid bits and update timestamps
Date: Wed, 29 May 2019 20:43:12 +0300	[thread overview]
Message-ID: <20190529174318.22424-9-amir73il@gmail.com> (raw)
In-Reply-To: <20190529174318.22424-1-amir73il@gmail.com>

Because generic_copy_file_range doesn't hold the destination inode lock
throughout the copy, strip setuid bits before and after copy.

The destination inode mtime is updated before and after the copy and the
source inode atime is updated after the copy, similar to
generic_file_read_iter().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/read_write.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index cec7e7b1f693..706ea5f276a7 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1590,8 +1590,27 @@ ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
 				struct file *file_out, loff_t pos_out,
 				size_t len, unsigned int flags)
 {
-	return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
-				len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
+	struct inode *inode_out = file_inode(file_out);
+	int ret, err;
+
+	/* Should inode_out lock be held throughout the copy operation? */
+	inode_lock(inode_out);
+	err = file_modified(file_out);
+	inode_unlock(inode_out);
+	if (err)
+		return err;
+
+	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
+			       len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
+
+	file_accessed(file_in);
+
+	/* To be on the safe side, remove privs also after copy */
+	inode_lock(inode_out);
+	err = file_modified(file_out);
+	inode_unlock(inode_out);
+
+	return err ?: ret;
 }
 EXPORT_SYMBOL(generic_copy_file_range);
 
-- 
2.17.1

