[RFC PATCH 1/5] ubifs: Implement POSIX Access Control Lists (ACLs)

From: Li Zetao
Date: Tue Mar 19 2024 - 12:24:43 EST


Implement the ACLs feature for ubifs based on vfs Posix ACLs,
details as follows:
* Initialize acl for newly created inode.
* Provides get/set interface to access ACLs.

ACLs feature relies on xattr implementation which using specific key
names "system.posix_acl_default" and "system.posix_acl_access". Now Only
the v2 version of POSIX ACLs is supported, and ubifs does not need to
customize the storage format, which can simplify the implementation.

Signed-off-by: Li Zetao <lizetao1@xxxxxxxxxx>
---
fs/ubifs/acl.c | 140 +++++++++++++++++++++++++++++++++++++++++++++++
fs/ubifs/ubifs.h | 13 +++++
fs/ubifs/xattr.c | 1 -
3 files changed, 153 insertions(+), 1 deletion(-)
create mode 100644 fs/ubifs/acl.c

diff --git a/fs/ubifs/acl.c b/fs/ubifs/acl.c
new file mode 100644
index 000000000000..253568baf097
--- /dev/null
+++ b/fs/ubifs/acl.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This file is part of UBIFS.
+ *
+ * Copyright (C) 2024 Huawei Tech. Co., Ltd.
+ *
+ * Authors: Li Zetao <lizetao1@xxxxxxxxxx>
+ */
+
+/* This file implements POSIX Access Control Lists (ACLs) */
+
+#include "ubifs.h"
+
+#include <linux/posix_acl_xattr.h>
+
+struct posix_acl *ubifs_get_inode_acl(struct inode *inode, int type, bool rcu)
+{
+ char *xattr_value = NULL;
+ const char *xattr_name;
+ struct posix_acl *acl;
+ ssize_t size;
+
+ if (rcu)
+ return ERR_PTR(-ECHILD);
+
+ xattr_name = posix_acl_xattr_name(type);
+ if (unlikely(!strcmp(xattr_name, "")))
+ return ERR_PTR(-EINVAL);
+
+ size = ubifs_xattr_get(inode, xattr_name, NULL, 0);
+ if (size > 0) {
+ xattr_value = kzalloc(size, GFP_KERNEL);
+ if (unlikely(!xattr_value))
+ return ERR_PTR(-ENOMEM);
+
+ size = ubifs_xattr_get(inode, xattr_name, xattr_value, size);
+ }
+
+ if (size > 0)
+ acl = posix_acl_from_xattr(&init_user_ns, xattr_value, size);
+ else if (size == -ENODATA || size == 0)
+ acl = NULL;
+ else
+ acl = ERR_PTR(size);
+
+ kfree(xattr_value);
+
+ return acl;
+}
+
+static int __ubifs_set_acl(struct inode *inode, int type, struct posix_acl *acl, int flags)
+{
+ void *xattr_value = NULL;
+ const char *xattr_name;
+ size_t size = 0;
+ int error;
+
+ xattr_name = posix_acl_xattr_name(type);
+ if (unlikely(!strcmp(xattr_name, "")))
+ return -EINVAL;
+
+ if (unlikely(!strcmp(xattr_name, XATTR_NAME_POSIX_ACL_DEFAULT) && !S_ISDIR(inode->i_mode)))
+ return acl ? -EACCES : 0;
+
+ if (acl) {
+ size = posix_acl_xattr_size(acl->a_count);
+ xattr_value = kmalloc(size, GFP_KERNEL);
+ if (unlikely(!xattr_value))
+ return -ENOMEM;
+
+ error = posix_acl_to_xattr(&init_user_ns, acl, xattr_value, size);
+ if (unlikely(error < 0))
+ goto out;
+ }
+
+ error = ubifs_xattr_set(inode, xattr_name, xattr_value, size, flags, false);
+ if (likely(!error))
+ set_cached_acl(inode, type, acl);
+out:
+ kfree(xattr_value);
+ return error;
+}
+
+int ubifs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, struct posix_acl *acl, int type)
+{
+ struct inode *inode = d_inode(dentry);
+ umode_t old_mode = inode->i_mode;
+ int error;
+
+ if (type == ACL_TYPE_ACCESS && acl) {
+ error = posix_acl_update_mode(idmap, inode, &inode->i_mode, &acl);
+ if (unlikely(error))
+ return error;
+ }
+
+ error = __ubifs_set_acl(inode, type, acl, 0);
+ if (unlikely(error))
+ inode->i_mode = old_mode;
+
+ return error;
+
+}
+
+/**
+ * ubifs_init_acl - initialize the ACLs for a new inode.
+ * @inode: newly created inode
+ * @dir: parent directory inode
+ *
+ * This function initialize ACLs, including inheriting the
+ * default ACLs of parent directory or modifying the default
+ * ACLs according to the mode parameter in open() / creat()
+ * system calls.
+ */
+int ubifs_init_acl(struct inode *inode, struct inode *dir)
+{
+ struct posix_acl *default_acl;
+ struct posix_acl *acl;
+ int error;
+
+ error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
+ if (unlikely(error))
+ return error;
+
+ if (default_acl) {
+ error = __ubifs_set_acl(inode, ACL_TYPE_DEFAULT, default_acl, XATTR_CREATE);
+ posix_acl_release(default_acl);
+ } else {
+ inode->i_default_acl = NULL;
+ }
+
+ if (acl) {
+ if (likely(!error))
+ error = __ubifs_set_acl(inode, ACL_TYPE_ACCESS, acl, XATTR_CREATE);
+ posix_acl_release(acl);
+ } else {
+ inode->i_acl = NULL;
+ }
+
+ return error;
+}
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 3916dc4f30ca..b0d3b076290d 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -2069,6 +2069,19 @@ static inline int ubifs_init_security(struct inode *dentry,
}
#endif

+#ifdef CONFIG_UBIFS_FS_POSIX_ACL
+struct posix_acl *ubifs_get_inode_acl(struct inode *inode, int type, bool rcu);
+int ubifs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, struct posix_acl *acl, int type);
+int ubifs_init_acl(struct inode *inode, struct inode *dir);
+
+#else /* CONFIG_UBIFS_FS_POSIX_ACL */
+#define ubifs_get_inode_acl NULL
+#define ubifs_set_acl NULL
+static inline int ubifs_init_acl(struct inode *inode, struct inode *dir)
+{
+ return 0;
+}
+#endif /* CONFIG_UBIFS_FS_POSIX_ACL */

/* super.c */
struct inode *ubifs_iget(struct super_block *sb, unsigned long inum);
diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c
index 0847db521984..eb1c1f5d10df 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -40,7 +40,6 @@
* in the VFS inode cache. The xentries are cached in the LNC cache (see
* tnc.c).
*
- * ACL support is not implemented.
*/

#include "ubifs.h"
--
2.34.1