fs: pass dentry to set acl method

The current way of setting and getting posix acls through the generic
xattr interface is error prone and type unsafe. The vfs needs to
interpret and fixup posix acls before storing or reporting it to
userspace. Various hacks exist to make this work. The code is hard to
understand and difficult to maintain in it's current form. Instead of
making this work by hacking posix acls through xattr handlers we are
building a dedicated posix acl api around the get and set inode
operations. This removes a lot of hackiness and makes the codepaths
easier to maintain. A lot of background can be found in [1].

Since some filesystem rely on the dentry being available to them when
setting posix acls (e.g., 9p and cifs) they cannot rely on set acl inode
operation. But since ->set_acl() is required in order to use the generic
posix acl xattr handlers filesystems that do not implement this inode
operation cannot use the handler and need to implement their own
dedicated posix acl handlers.

Update the ->set_acl() inode method to take a dentry argument. This
allows all filesystems to rely on ->set_acl().

As far as I can tell all codepaths can be switched to rely on the dentry
instead of just the inode. Note that the original motivation for passing
the dentry separate from the inode instead of just the dentry in the
xattr handlers was because of security modules that call
security_d_instantiate(). This hook is called during
d_instantiate_new(), d_add(), __d_instantiate_anon(), and
d_splice_alias() to initialize the inode's security context and possibly
to set security.* xattrs. Since this only affects security.* xattrs this
is completely irrelevant for posix acls.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

4 files changed, 14 insertions, 13 deletions

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index b2fc85d440d0..2466edc57424 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -2956,7 +2956,7 @@ int smb2_open(struct ksmbd_work *work)
 		struct inode *inode = d_inode(path.dentry);
 
 		posix_acl_rc = ksmbd_vfs_inherit_posix_acl(user_ns,
-							   inode,
+							   path.dentry,
 							   d_inode(path.dentry->d_parent));
 		if (posix_acl_rc)
 			ksmbd_debug(SMB, "inherit posix acl failed : %d\n", posix_acl_rc);
@@ -2972,7 +2972,7 @@ int smb2_open(struct ksmbd_work *work)
 			if (rc) {
 				if (posix_acl_rc)
 					ksmbd_vfs_set_init_posix_acl(user_ns,
-								     inode);
+								     path.dentry);
 
 				if (test_share_config_flag(work->tcon->share_conf,
 							   KSMBD_SHARE_FLAG_ACL_XATTR)) {
diff --git a/fs/ksmbd/smbacl.c b/fs/ksmbd/smbacl.c
index b05ff9b146b5..a1e05fe997fe 100644
--- a/fs/ksmbd/smbacl.c
+++ b/fs/ksmbd/smbacl.c
@@ -1386,14 +1386,14 @@ int set_info_sec(struct ksmbd_conn *conn, struct ksmbd_tree_connect *tcon,
 	ksmbd_vfs_remove_acl_xattrs(user_ns, path->dentry);
 	/* Update posix acls */
 	if (IS_ENABLED(CONFIG_FS_POSIX_ACL) && fattr.cf_dacls) {
-		rc = set_posix_acl(user_ns, inode,
+		rc = set_posix_acl(user_ns, path->dentry,
 				   ACL_TYPE_ACCESS, fattr.cf_acls);
 		if (rc < 0)
 			ksmbd_debug(SMB,
 				    "Set posix acl(ACL_TYPE_ACCESS) failed, rc : %d\n",
 				    rc);
 		if (S_ISDIR(inode->i_mode) && fattr.cf_dacls) {
-			rc = set_posix_acl(user_ns, inode,
+			rc = set_posix_acl(user_ns, path->dentry,
 					   ACL_TYPE_DEFAULT, fattr.cf_dacls);
 			if (rc)
 				ksmbd_debug(SMB,
diff --git a/fs/ksmbd/vfs.c b/fs/ksmbd/vfs.c
index 8de970d6146f..7dee8b78762d 100644
--- a/fs/ksmbd/vfs.c
+++ b/fs/ksmbd/vfs.c
@@ -1824,10 +1824,11 @@ void ksmbd_vfs_posix_lock_unblock(struct file_lock *flock)
 }
 
 int ksmbd_vfs_set_init_posix_acl(struct user_namespace *user_ns,
-				 struct inode *inode)
+				 struct dentry *dentry)
 {
 	struct posix_acl_state acl_state;
 	struct posix_acl *acls;
+	struct inode *inode = d_inode(dentry);
 	int rc;
 
 	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL))
@@ -1856,14 +1857,13 @@ int ksmbd_vfs_set_init_posix_acl(struct user_namespace *user_ns,
 		return -ENOMEM;
 	}
 	posix_state_to_acl(&acl_state, acls->a_entries);
-	rc = set_posix_acl(user_ns, inode, ACL_TYPE_ACCESS, acls);
+	rc = set_posix_acl(user_ns, dentry, ACL_TYPE_ACCESS, acls);
 	if (rc < 0)
 		ksmbd_debug(SMB, "Set posix acl(ACL_TYPE_ACCESS) failed, rc : %d\n",
 			    rc);
 	else if (S_ISDIR(inode->i_mode)) {
 		posix_state_to_acl(&acl_state, acls->a_entries);
-		rc = set_posix_acl(user_ns, inode, ACL_TYPE_DEFAULT,
-				   acls);
+		rc = set_posix_acl(user_ns, dentry, ACL_TYPE_DEFAULT, acls);
 		if (rc < 0)
 			ksmbd_debug(SMB, "Set posix acl(ACL_TYPE_DEFAULT) failed, rc : %d\n",
 				    rc);
@@ -1874,10 +1874,11 @@ int ksmbd_vfs_set_init_posix_acl(struct user_namespace *user_ns,
 }
 
 int ksmbd_vfs_inherit_posix_acl(struct user_namespace *user_ns,
-				struct inode *inode, struct inode *parent_inode)
+				struct dentry *dentry, struct inode *parent_inode)
 {
 	struct posix_acl *acls;
 	struct posix_acl_entry *pace;
+	struct inode *inode = d_inode(dentry);
 	int rc, i;
 
 	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL))
@@ -1895,12 +1896,12 @@ int ksmbd_vfs_inherit_posix_acl(struct user_namespace *user_ns,
 		}
 	}
 
-	rc = set_posix_acl(user_ns, inode, ACL_TYPE_ACCESS, acls);
+	rc = set_posix_acl(user_ns, dentry, ACL_TYPE_ACCESS, acls);
 	if (rc < 0)
 		ksmbd_debug(SMB, "Set posix acl(ACL_TYPE_ACCESS) failed, rc : %d\n",
 			    rc);
 	if (S_ISDIR(inode->i_mode)) {
-		rc = set_posix_acl(user_ns, inode, ACL_TYPE_DEFAULT,
+		rc = set_posix_acl(user_ns, dentry, ACL_TYPE_DEFAULT,
 				   acls);
 		if (rc < 0)
 			ksmbd_debug(SMB, "Set posix acl(ACL_TYPE_DEFAULT) failed, rc : %d\n",
diff --git a/fs/ksmbd/vfs.h b/fs/ksmbd/vfs.h
index 593059ca8511..0d73d735cc39 100644
--- a/fs/ksmbd/vfs.h
+++ b/fs/ksmbd/vfs.h
@@ -160,8 +160,8 @@ int ksmbd_vfs_get_dos_attrib_xattr(struct user_namespace *user_ns,
 				   struct dentry *dentry,
 				   struct xattr_dos_attrib *da);
 int ksmbd_vfs_set_init_posix_acl(struct user_namespace *user_ns,
-				 struct inode *inode);
+				 struct dentry *dentry);
 int ksmbd_vfs_inherit_posix_acl(struct user_namespace *user_ns,
-				struct inode *inode,
+				struct dentry *dentry,
 				struct inode *parent_inode);
 #endif /* __KSMBD_VFS_H__ */