ceph: don't clobber i_snap_caps on non-I_NEW inode

stable inclusion
from stable-5.10.39
commit db275714dd506db541f4a17f1549a2ec7f8d3ef6
bugzilla: 51881
CVE: NA

--------------------------------

[ Upstream commit d3c51ae1 ]

We want the snapdir to mirror the non-snapped directory's attributes for
most things, but i_snap_caps represents the caps granted on the snapshot
directory by the MDS itself. A misbehaving MDS could issue different
caps for the snapdir and we lose them here.

Only reset i_snap_caps when the inode is I_NEW. Also, move the setting
of i_op and i_fop inside the if block since they should never change
anyway.
Reported-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NJeff Layton <jlayton@kernel.org>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/ceph/inode.c

@@ -87,14 +87,15 @@ struct inode *ceph_get_snapdir(struct inode *parent)
 	inode->i_mtime = parent->i_mtime;
 	inode->i_ctime = parent->i_ctime;
 	inode->i_atime = parent->i_atime;
-	inode->i_op = &ceph_snapdir_iops;
-	inode->i_fop = &ceph_snapdir_fops;
-	ci->i_snap_caps = CEPH_CAP_PIN; /* so we can open */
 	ci->i_rbytes = 0;
 	ci->i_btime = ceph_inode(parent)->i_btime;
 
-	if (inode->i_state & I_NEW)
+	if (inode->i_state & I_NEW) {
+		inode->i_op = &ceph_snapdir_iops;
+		inode->i_fop = &ceph_snapdir_fops;
+		ci->i_snap_caps = CEPH_CAP_PIN; /* so we can open */
 		unlock_new_inode(inode);
+	}
 
 	return inode;
 }