linux-kernel - [RFC][PATCH 5/5] ramfs: Initialize security of in-memory inodes

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Message-Id: <20230607123612.2791303-6-roberto.sassu@huaweicloud.com>
Date:   Wed,  7 Jun 2023 14:36:12 +0200
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     casey@...aufler-ca.com, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com
Cc:     linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [RFC][PATCH 5/5] ramfs: Initialize security of in-memory inodes

From: Roberto Sassu <roberto.sassu@...wei.com>

Add a call security_inode_init_security() after ramfs_get_inode(), to let
LSMs initialize the inode security field. Skip ramfs_fill_super(), as the
initialization is done through the sb_set_mnt_opts hook.

Calling security_inode_init_security() call inside ramfs_get_inode() is
not possible since, for CONFIG_SHMEM=n, tmpfs also calls the former after
the latter.

Pass NULL as initxattrs() callback to security_inode_init_security(), since
the purpose of the call is only to initialize the in-memory inodes.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 fs/ramfs/inode.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 5ba580c7883..e6b5f04b2b2 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -102,6 +102,14 @@ ramfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	int error = -ENOSPC;
 
 	if (inode) {
+		error = security_inode_init_security(inode, dir,
+						     &dentry->d_name, NULL,
+						     NULL);
+		if (error && error != -EOPNOTSUPP) {
+			iput(inode);
+			return error;
+		}
+
 		d_instantiate(dentry, inode);
 		dget(dentry);	/* Extra count - pin the dentry in core */
 		error = 0;
@@ -134,6 +142,15 @@ static int ramfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 	inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
 	if (inode) {
 		int l = strlen(symname)+1;
+
+		error = security_inode_init_security(inode, dir,
+						     &dentry->d_name, NULL,
+						     NULL);
+		if (error && error != -EOPNOTSUPP) {
+			iput(inode);
+			return error;
+		}
+
 		error = page_symlink(inode, symname, l);
 		if (!error) {
 			d_instantiate(dentry, inode);
@@ -149,10 +166,20 @@ static int ramfs_tmpfile(struct mnt_idmap *idmap,
 			 struct inode *dir, struct file *file, umode_t mode)
 {
 	struct inode *inode;
+	int error;
 
 	inode = ramfs_get_inode(dir->i_sb, dir, mode, 0);
 	if (!inode)
 		return -ENOSPC;
+
+	error = security_inode_init_security(inode, dir,
+					     &file_dentry(file)->d_name, NULL,
+					     NULL);
+	if (error && error != -EOPNOTSUPP) {
+		iput(inode);
+		return error;
+	}
+
 	d_tmpfile(file, inode);
 	return finish_open_simple(file, 0);
 }
-- 
2.25.1