linux-kernel - [PATCH v6 07/11] LSM: Helpers for attribute names and filling an lsm

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Message-Id: <20230222200838.8149-8-casey@schaufler-ca.com>
Date:   Wed, 22 Feb 2023 12:08:34 -0800
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     casey@...aufler-ca.com, paul@...l-moore.com,
        linux-security-module@...r.kernel.org
Cc:     jmorris@...ei.org, keescook@...omium.org,
        john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
        stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, mic@...ikod.net
Subject: [PATCH v6 07/11] LSM: Helpers for attribute names and filling an lsm_ctx

Add lsm_name_to_attr(), which translates a text string to a
LSM_ATTR value if one is available.

Add lsm_fill_user_ctx(), which fills a struct lsm_ctx, including
the trailing attribute value.

Both are used in module specific components of LSM system calls.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
 include/linux/security.h | 13 +++++++++++++
 security/security.c      | 31 +++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index 21971a635b6a..bf615981b147 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -264,6 +264,7 @@ int unregister_blocking_lsm_notifier(struct notifier_block *nb);
 /* prototypes */
 extern int security_init(void);
 extern int early_security_init(void);
+extern u64 lsm_name_to_attr(const char *name);
 
 /* Security operations */
 int security_binder_set_context_mgr(const struct cred *mgr);
@@ -493,6 +494,8 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
 int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
 int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
 int security_locked_down(enum lockdown_reason what);
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+		      size_t context_size, u64 id, u64 flags);
 #else /* CONFIG_SECURITY */
 
 static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -510,6 +513,11 @@ static inline  int unregister_blocking_lsm_notifier(struct notifier_block *nb)
 	return 0;
 }
 
+static inline u64 lsm_name_to_attr(const char *name)
+{
+	return 0;
+}
+
 static inline void security_free_mnt_opts(void **mnt_opts)
 {
 }
@@ -1422,6 +1430,11 @@ static inline int security_locked_down(enum lockdown_reason what)
 {
 	return 0;
 }
+static inline int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+				    size_t context_size, u64 id, u64 flags)
+{
+	return 0;
+}
 #endif	/* CONFIG_SECURITY */
 
 #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/security/security.c b/security/security.c
index 6823a6cb32a9..48c883c8d340 100644
--- a/security/security.c
+++ b/security/security.c
@@ -753,6 +753,37 @@ static int lsm_superblock_alloc(struct super_block *sb)
 	return 0;
 }
 
+/**
+ * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
+ * @ctx: an LSM context to be filled
+ * @context: the new context value
+ * @context_size: the size of the new context value
+ * @id: LSM id
+ * @flags: LSM defined flags
+ *
+ * Fill all of the fields in a user space lsm_ctx structure.
+ * Caller is assumed to have verified that @ctx has enough space
+ * for @context.
+ * Returns 0 on success, -EFAULT on a copyout error.
+ */
+int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context,
+		      size_t context_size, u64 id, u64 flags)
+{
+	struct lsm_ctx local;
+	void __user *vc = ctx;
+
+	local.id = id;
+	local.flags = flags;
+	local.ctx_len = context_size;
+	local.len = context_size + sizeof(local);
+	vc += sizeof(local);
+	if (copy_to_user(ctx, &local, sizeof(local)))
+		return -EFAULT;
+	if (context_size > 0 && copy_to_user(vc, context, context_size))
+		return -EFAULT;
+	return 0;
+}
+
 /*
  * The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
  * can be accessed with:
-- 
2.39.0