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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hu Weiwen <sehuww@mail.scut.edu.cn>,
        Xiubo Li <xiubli@redhat.com>, Ilya Dryomov <idryomov@gmail.com>
Subject: [PATCH 4.19 021/229] ceph: dont truncate file in atomic_open
Date:   Mon, 24 Oct 2022 13:29:00 +0200
Message-Id: <20221024112959.826609588@linuxfoundation.org>
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From: Hu Weiwen <sehuww@mail.scut.edu.cn>

commit 7cb9994754f8a36ae9e5ec4597c5c4c2d6c03832 upstream.

Clear O_TRUNC from the flags sent in the MDS create request.

`atomic_open' is called before permission check. We should not do any
modification to the file here. The caller will do the truncation
afterward.

Fixes: 124e68e74099 ("ceph: file operations")
Signed-off-by: Hu Weiwen <sehuww@mail.scut.edu.cn>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
[Xiubo: fixed a trivial conflict for 5.10 backport]
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ceph/file.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -446,6 +446,12 @@ int ceph_atomic_open(struct inode *dir,
 	if (dentry->d_name.len > NAME_MAX)
 		return -ENAMETOOLONG;
 
+	/*
+	 * Do not truncate the file, since atomic_open is called before the
+	 * permission check. The caller will do the truncation afterward.
+	 */
+	flags &= ~O_TRUNC;
+
 	if (flags & O_CREAT) {
 		if (ceph_quota_is_max_files_exceeded(dir))
 			return -EDQUOT;
@@ -478,9 +484,7 @@ int ceph_atomic_open(struct inode *dir,
 
 	req->r_parent = dir;
 	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
-	err = ceph_mdsc_do_request(mdsc,
-				   (flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
-				   req);
+	err = ceph_mdsc_do_request(mdsc, (flags & O_CREAT) ? dir : NULL, req);
 	err = ceph_handle_snapdir(req, dentry, err);
 	if (err)
 		goto out_req;