[Ocfs2-devel] [PATCH v7 2/6] ocfs2: Switch to security_inode_init_security()

[Roberto Sassu via Ocfs2-devel <ocfs2-devel@oss.oracle.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, modify the handling of the return value from
ocfs2_init_security_get(). As security_inode_init_security() does not
return -EOPNOTSUPP, remove this case and directly handle the error if the
return value is not zero.

However, the previous case of receiving -EOPNOTSUPP should be still
taken into account, as security_inode_init_security() could return zero
without setting xattrs and ocfs2 would consider it as if the xattr was set.

Instead, if security_inode_init_security() returned zero, look at the xattr
if it was set, and behave accordingly, i.e. set si->enable to zero to
notify to the functions following ocfs2_init_security_get() that the xattr
is not available (same as if security_old_inode_init_security() returned
-EOPNOTSUPP).

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
---
 fs/ocfs2/namei.c | 18 ++++++------------
 fs/ocfs2/xattr.c | 30 ++++++++++++++++++++++++++----
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 05f32989bad6..55fba81cd2d1 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -242,6 +242,7 @@ static int ocfs2_mknod(struct user_namespace *mnt_userns,
 	int want_meta = 0;
 	int xattr_credits = 0;
 	struct ocfs2_security_xattr_info si = {
+		.name = NULL,
 		.enable = 1,
 	};
 	int did_quota_inode = 0;
@@ -315,12 +316,8 @@ static int ocfs2_mknod(struct user_namespace *mnt_userns,
 	/* get security xattr */
 	status = ocfs2_init_security_get(inode, dir, &dentry->d_name, &si);
 	if (status) {
-		if (status == -EOPNOTSUPP)
-			si.enable = 0;
-		else {
-			mlog_errno(status);
-			goto leave;
-		}
+		mlog_errno(status);
+		goto leave;
 	}
 
 	/* calculate meta data/clusters for setting security and acl xattr */
@@ -1805,6 +1802,7 @@ static int ocfs2_symlink(struct user_namespace *mnt_userns,
 	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;
@@ -1875,12 +1873,8 @@ static int ocfs2_symlink(struct user_namespace *mnt_userns,
 	/* get security xattr */
 	status = ocfs2_init_security_get(inode, dir, &dentry->d_name, &si);
 	if (status) {
-		if (status == -EOPNOTSUPP)
-			si.enable = 0;
-		else {
-			mlog_errno(status);
-			goto bail;
-		}
+		mlog_errno(status);
+		goto bail;
 	}
 
 	/* calculate meta data/clusters for setting security xattr */
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 95d0611c5fc7..55699c573541 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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