linux-kernel - [PATCH v8 08/19] ima: Use mac_admin_ns_capable() to check corresponding capability

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Date:   Tue,  4 Jan 2022 12:04:05 -0500
From:   Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     zohar@...ux.ibm.com, serge@...lyn.com,
        christian.brauner@...ntu.com, containers@...ts.linux.dev,
        dmitry.kasatkin@...il.com, ebiederm@...ssion.com,
        krzysztof.struczynski@...wei.com, roberto.sassu@...wei.com,
        mpeters@...hat.com, lhinds@...hat.com, lsturman@...hat.com,
        puiterwi@...hat.com, jejb@...ux.ibm.com, jamjoom@...ibm.com,
        linux-kernel@...r.kernel.org, paul@...l-moore.com, rgb@...hat.com,
        linux-security-module@...r.kernel.org, jmorris@...ei.org,
        Stefan Berger <stefanb@...ux.ibm.com>,
        Denis Semakin <denis.semakin@...wei.com>
Subject: [PATCH v8 08/19] ima: Use mac_admin_ns_capable() to check corresponding capability

From: Stefan Berger <stefanb@...ux.ibm.com>

Use mac_admin_ns_capable() to check corresponding capability to allow
read/write IMA policy without CAP_SYS_ADMIN but with CAP_MAC_ADMIN.

Signed-off-by: Denis Semakin <denis.semakin@...wei.com>
Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
---
 include/linux/capability.h      | 6 ++++++
 security/integrity/ima/ima.h    | 6 ++++++
 security/integrity/ima/ima_fs.c | 3 ++-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 65efb74c3585..991579178f32 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -270,6 +270,12 @@ static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns)
 		ns_capable(ns, CAP_SYS_ADMIN);
 }
 
+static inline bool mac_admin_ns_capable(struct user_namespace *ns)
+{
+	return ns_capable(ns, CAP_MAC_ADMIN) ||
+		ns_capable(ns, CAP_SYS_ADMIN);
+}
+
 /* audit system wants to get cap info from files as well */
 int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
 			   const struct dentry *dentry,
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 224b09617c52..0c86a955cedf 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -483,6 +483,12 @@ static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op,
 #define	POLICY_FILE_FLAGS	S_IWUSR
 #endif /* CONFIG_IMA_READ_POLICY */
 
+static inline
+struct user_namespace *ima_user_ns_from_file(const struct file *filp)
+{
+	return file_inode(filp)->i_sb->s_user_ns;
+}
+
 static inline struct ima_namespace *get_current_ns(void)
 {
 	return &init_ima_ns;
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 5b6404991b37..71302bb5427f 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -377,6 +377,7 @@ static const struct seq_operations ima_policy_seqops = {
  */
 static int ima_open_policy(struct inode *inode, struct file *filp)
 {
+	struct user_namespace *user_ns = ima_user_ns_from_file(filp);
 	struct ima_namespace *ns = &init_ima_ns;
 
 	if (!(filp->f_flags & O_WRONLY)) {
@@ -385,7 +386,7 @@ static int ima_open_policy(struct inode *inode, struct file *filp)
 #else
 		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 			return -EACCES;
-		if (!capable(CAP_SYS_ADMIN))
+		if (!mac_admin_ns_capable(user_ns))
 			return -EPERM;
 		return seq_open(filp, &ima_policy_seqops);
 #endif
-- 
2.31.1