linux-kernel - [PATCH v2 04/13] Audit: maintain an lsmblob in audit

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Message-ID: <20240830003411.16818-5-casey@schaufler-ca.com>
Date: Thu, 29 Aug 2024 17:34:02 -0700
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,
	serge@...lyn.com,
	keescook@...omium.org,
	john.johansen@...onical.com,
	penguin-kernel@...ove.sakura.ne.jp,
	stephen.smalley.work@...il.com,
	linux-kernel@...r.kernel.org,
	selinux@...r.kernel.org,
	mic@...ikod.net
Subject: [PATCH v2 04/13] Audit: maintain an lsmblob in audit_context

Replace the secid value stored in struct audit_context with a struct
lsmblob. Change the code that uses this value to accommodate the
change. security_audit_rule_match() expects a lsmblob, so existing
scaffolding can be removed. A call to security_secid_to_secctx()
is changed to security_lsmblob_to_secctx().  The call to
security_ipc_getsecid() is scaffolded.

A new function lsmblob_is_set() is introduced to identify whether
an lsmblob contains a non-zero value.

Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
 include/linux/security.h | 13 +++++++++++++
 kernel/audit.h           |  3 ++-
 kernel/auditsc.c         | 19 ++++++++-----------
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index 457fafc32fb0..a0b23b6e8734 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -277,6 +277,19 @@ static inline const char *kernel_load_data_id_str(enum kernel_load_data_id id)
 	return kernel_load_data_str[id];
 }
 
+/**
+ * lsmblob_is_set - report if there is a value in the lsmblob
+ * @blob: Pointer to the exported LSM data
+ *
+ * Returns true if there is a value set, false otherwise
+ */
+static inline bool lsmblob_is_set(struct lsmblob *blob)
+{
+	const struct lsmblob empty = {};
+
+	return !!memcmp(blob, &empty, sizeof(*blob));
+}
+
 #ifdef CONFIG_SECURITY
 
 int call_blocking_lsm_notifier(enum lsm_event event, void *data);
diff --git a/kernel/audit.h b/kernel/audit.h
index a60d2840559e..b1f2de4d4f1e 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -11,6 +11,7 @@
 
 #include <linux/fs.h>
 #include <linux/audit.h>
+#include <linux/security.h>
 #include <linux/skbuff.h>
 #include <uapi/linux/mqueue.h>
 #include <linux/tty.h>
@@ -160,7 +161,7 @@ struct audit_context {
 			kuid_t			uid;
 			kgid_t			gid;
 			umode_t			mode;
-			u32			osid;
+			struct lsmblob		oblob;
 			int			has_perm;
 			uid_t			perm_uid;
 			gid_t			perm_gid;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 23adb15cae43..84f6e9356b8f 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -724,9 +724,7 @@ static int audit_filter_rules(struct task_struct *tsk,
 				/* Find ipc objects that match */
 				if (!ctx || ctx->type != AUDIT_IPC)
 					break;
-				/* scaffolding */
-				blob.scaffold.secid = ctx->ipc.osid;
-				if (security_audit_rule_match(&blob,
+				if (security_audit_rule_match(&ctx->ipc.oblob,
 							      f->type, f->op,
 							      f->lsm_rule))
 					++result;
@@ -1394,19 +1392,17 @@ static void show_special(struct audit_context *context, int *call_panic)
 			audit_log_format(ab, " a%d=%lx", i,
 				context->socketcall.args[i]);
 		break; }
-	case AUDIT_IPC: {
-		u32 osid = context->ipc.osid;
-
+	case AUDIT_IPC:
 		audit_log_format(ab, "ouid=%u ogid=%u mode=%#ho",
 				 from_kuid(&init_user_ns, context->ipc.uid),
 				 from_kgid(&init_user_ns, context->ipc.gid),
 				 context->ipc.mode);
-		if (osid) {
+		if (lsmblob_is_set(&context->ipc.oblob)) {
 			char *ctx = NULL;
 			u32 len;
 
-			if (security_secid_to_secctx(osid, &ctx, &len)) {
-				audit_log_format(ab, " osid=%u", osid);
+			if (security_lsmblob_to_secctx(&context->ipc.oblob,
+						       &ctx, &len)) {
 				*call_panic = 1;
 			} else {
 				audit_log_format(ab, " obj=%s", ctx);
@@ -1426,7 +1422,7 @@ static void show_special(struct audit_context *context, int *call_panic)
 				context->ipc.perm_gid,
 				context->ipc.perm_mode);
 		}
-		break; }
+		break;
 	case AUDIT_MQ_OPEN:
 		audit_log_format(ab,
 			"oflag=0x%x mode=%#ho mq_flags=0x%lx mq_maxmsg=%ld "
@@ -2642,7 +2638,8 @@ void __audit_ipc_obj(struct kern_ipc_perm *ipcp)
 	context->ipc.gid = ipcp->gid;
 	context->ipc.mode = ipcp->mode;
 	context->ipc.has_perm = 0;
-	security_ipc_getsecid(ipcp, &context->ipc.osid);
+	/* scaffolding */
+	security_ipc_getsecid(ipcp, &context->ipc.oblob.scaffold.secid);
 	context->type = AUDIT_IPC;
 }
 
-- 
2.46.0