ovl: let helper ovl_i_path_real() return the realinode

Let helper ovl_i_path_real() return the realinode to prepare for
checking non-null realinode in RCU walking path.

[msz] Use d_inode_rcu() since we are depending on the consitency
between dentry and inode being non-NULL in an RCU setting.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Fixes: ffa5723c6d25 ("ovl: store lower path in ovl_inode")
Cc: <stable@vger.kernel.org> # v5.19
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 4d0b278..7398de3 100644 (file)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -382,7 +382,7 @@ enum ovl_path_type ovl_path_type(struct dentry *dentry);
 void ovl_path_upper(struct dentry *dentry, struct path *path);
 void ovl_path_lower(struct dentry *dentry, struct path *path);
 void ovl_path_lowerdata(struct dentry *dentry, struct path *path);
-void ovl_i_path_real(struct inode *inode, struct path *path);
+struct inode *ovl_i_path_real(struct inode *inode, struct path *path);
 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
 enum ovl_path_type ovl_path_realdata(struct dentry *dentry, struct path *path);
 struct dentry *ovl_dentry_upper(struct dentry *dentry);

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 923d66d..5a6f34c 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -250,7 +250,7 @@ struct dentry *ovl_i_dentry_upper(struct inode *inode)
        return ovl_upperdentry_dereference(OVL_I(inode));
 }
 
-void ovl_i_path_real(struct inode *inode, struct path *path)
+struct inode *ovl_i_path_real(struct inode *inode, struct path *path)
 {
        path->dentry = ovl_i_dentry_upper(inode);
        if (!path->dentry) {
@@ -259,6 +259,8 @@ void ovl_i_path_real(struct inode *inode, struct path *path)
        } else {
                path->mnt = ovl_upper_mnt(OVL_FS(inode->i_sb));
        }
+
+       return path->dentry ? d_inode_rcu(path->dentry) : NULL;
 }
 
 struct inode *ovl_inode_upper(struct inode *inode)
@@ -1105,8 +1107,7 @@ void ovl_copyattr(struct inode *inode)
        vfsuid_t vfsuid;
        vfsgid_t vfsgid;
 
-       ovl_i_path_real(inode, &realpath);
-       realinode = d_inode(realpath.dentry);
+       realinode = ovl_i_path_real(inode, &realpath);
        real_idmap = mnt_idmap(realpath.mnt);
 
        vfsuid = i_uid_into_vfsuid(real_idmap, realinode);