[Ocfs2-devel] [PATCH v8 2/6] ocfs2: Switch to security_inode_init_security() - Roberto Sassu via Ocfs2-devel

From: Roberto Sassu via Ocfs2-devel <ocfs2-devel@oss.oracle.com>
To: mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com,
	zohar@linux.ibm.com, dmitry.kasatkin@gmail.com,
	paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com,
	stephen.smalley.work@gmail.com, eparis@parisplace.org,
	casey@schaufler-ca.com
Cc: nicolas.bouchinet@clip-os.org, keescook@chromium.org,
	selinux@vger.kernel.org, Roberto Sassu <roberto.sassu@huawei.com>,
	reiserfs-devel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-integrity@vger.kernel.org, ocfs2-devel@oss.oracle.com
Subject: [Ocfs2-devel] [PATCH v8 2/6] ocfs2: Switch to security_inode_init_security()
Date: Tue, 14 Mar 2023 09:17:16 +0100	[thread overview]
Message-ID: <20230314081720.4158676-3-roberto.sassu@huaweicloud.com> (raw)
In-Reply-To: <20230314081720.4158676-1-roberto.sassu@huaweicloud.com>

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

In preparation for removing security_old_inode_init_security(), switch to
security_inode_init_security().

Extend the existing ocfs2_initxattrs() to take the
ocfs2_security_xattr_info structure from fs_info, and populate the
name/value/len triple with the first xattr provided by LSMs.

As fs_info was not used before, ocfs2_initxattrs() can now handle the case
of replicating the behavior of security_old_inode_init_security(), i.e.
just obtaining the xattr, in addition to setting all xattrs provided by
LSMs.

Supporting multiple xattrs is not currently supported where
security_old_inode_init_security() was called (mknod, symlink), as it
requires non-trivial changes that can be done at a later time. Like for
reiserfs, even if EVM is invoked, it will not provide an xattr (if it is
not the first to set it, its xattr will be discarded; if it is the first,
it does not have xattrs to calculate the HMAC on).

Finally, since security_inode_init_security(), unlike
security_old_inode_init_security(), returns zero instead of -EOPNOTSUPP if
no xattrs were provided by LSMs or if inodes are private, additionally
check in ocfs2_init_security_get() if the xattr name is set.

If not, act as if security_old_inode_init_security() returned -EOPNOTSUPP,
and set si->enable to zero to notify to the functions following
ocfs2_init_security_get() that no xattrs are available.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com>
---
 fs/ocfs2/namei.c |  2 ++
 fs/ocfs2/xattr.c | 30 ++++++++++++++++++++++++++----
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 9175dbc4720..17c52225b87 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -242,6 +242,7 @@ static int ocfs2_mknod(struct mnt_idmap *idmap,
 	int want_meta = 0;
 	int xattr_credits = 0;
 	struct ocfs2_security_xattr_info si = {
+		.name = NULL,
 		.enable = 1,
 	};
 	int did_quota_inode = 0;
@@ -1805,6 +1806,7 @@ static int ocfs2_symlink(struct mnt_idmap *idmap,
 	int want_clusters = 0;
 	int xattr_credits = 0;
 	struct ocfs2_security_xattr_info si = {
+		.name = NULL,
 		.enable = 1,
 	};
 	int did_quota = 0, did_quota_inode = 0;
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 389308efe85..469ec45baee 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -7259,9 +7259,21 @@ static int ocfs2_xattr_security_set(const struct xattr_handler *handler,
 static int ocfs2_initxattrs(struct inode *inode, const struct xattr *xattr_array,
 		     void *fs_info)
 {
+	struct ocfs2_security_xattr_info *si = fs_info;
 	const struct xattr *xattr;
 	int err = 0;
 
+	if (si) {
+		si->value = kmemdup(xattr_array->value, xattr_array->value_len,
+				    GFP_KERNEL);
+		if (!si->value)
+			return -ENOMEM;
+
+		si->name = xattr_array->name;
+		si->value_len = xattr_array->value_len;
+		return 0;
+	}
+
 	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 		err = ocfs2_xattr_set(inode, OCFS2_XATTR_INDEX_SECURITY,
 				      xattr->name, xattr->value,
@@ -7277,13 +7289,23 @@ int ocfs2_init_security_get(struct inode *inode,
 			    const struct qstr *qstr,
 			    struct ocfs2_security_xattr_info *si)
 {
+	int ret;
+
 	/* check whether ocfs2 support feature xattr */
 	if (!ocfs2_supports_xattr(OCFS2_SB(dir->i_sb)))
 		return -EOPNOTSUPP;
-	if (si)
-		return security_old_inode_init_security(inode, dir, qstr,
-							&si->name, &si->value,
-							&si->value_len);
+	if (si) {
+		ret = security_inode_init_security(inode, dir, qstr,
+						   &ocfs2_initxattrs, si);
+		/*
+		 * security_inode_init_security() does not return -EOPNOTSUPP,
+		 * we have to check the xattr ourselves.
+		 */
+		if (!ret && !si->name)
+			si->enable = 0;
+
+		return ret;
+	}
 
 	return security_inode_init_security(inode, dir, qstr,
 					    &ocfs2_initxattrs, NULL);
-- 
2.25.1


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