[PATCH ghak90 v10 05/11] audit: add support for non-syscall auxiliary records

[Richard Guy Briggs]

Standalone audit records have the timestamp and serial number generated
on the fly and as such are unique, making them standalone.  This new
function audit_alloc_local() generates a local audit context that will
be used only for a standalone record and its auxiliary record(s).  The
context is discarded immediately after the local associated records are
produced.

A new flag, "local" was used rather than "in_syscall" since it would be
overloading the original purpose and meaning.  Events using this
function may not be triggered by a syscall but still need records
linked by timestamp and serial.

Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
Acked-by: Serge Hallyn <serge@xxxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Reviewed-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
 include/linux/audit.h |  8 ++++++++
 kernel/audit.h        |  1 +
 kernel/auditsc.c      | 31 ++++++++++++++++++++++++++-----
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 7c1928e75cfe..9f0238f7960f 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -304,6 +304,8 @@ static inline int audit_signal_info(int sig, struct task_struct *t)
 
 /* These are defined in auditsc.c */
 				/* Public API */
+extern struct audit_context *audit_alloc_local(gfp_t gfpflags);
+extern void audit_free_context(struct audit_context *context);
 extern void __audit_syscall_entry(int major, unsigned long a0, unsigned long a1,
 				  unsigned long a2, unsigned long a3);
 extern void __audit_syscall_exit(int ret_success, long ret_value);
@@ -555,6 +557,12 @@ static inline void audit_log_nfcfg(const char *name, u8 af,
 extern int audit_n_rules;
 extern int audit_signals;
 #else /* CONFIG_AUDITSYSCALL */
+static inline struct audit_context *audit_alloc_local(gfp_t gfpflags)
+{
+	return NULL;
+}
+static inline void audit_free_context(struct audit_context *context)
+{ }
 static inline void audit_syscall_entry(int major, unsigned long a0,
 				       unsigned long a1, unsigned long a2,
 				       unsigned long a3)
diff --git a/kernel/audit.h b/kernel/audit.h
index de79f59d623f..40e609787a0c 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -98,6 +98,7 @@ struct audit_proctitle {
 struct audit_context {
 	int		    dummy;	/* must be the first element */
 	int		    in_syscall;	/* 1 if task is in a syscall */
+	bool		    local;	/* local context needed */
 	enum audit_state    state, current_state;
 	unsigned int	    serial;     /* serial number for record */
 	int		    major;      /* syscall number */
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index eecc7b2e29a7..df26d0aa5e6d 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -920,11 +920,12 @@ static inline void audit_free_aux(struct audit_context *context)
 	}
 }
 
-static inline struct audit_context *audit_alloc_context(enum audit_state state)
+static inline struct audit_context *audit_alloc_context(enum audit_state state,
+							gfp_t gfpflags)
 {
 	struct audit_context *context;
 
-	context = kzalloc(sizeof(*context), GFP_KERNEL);
+	context = kzalloc(sizeof(*context), gfpflags);
 	if (!context)
 		return NULL;
 	context->state = state;
@@ -962,7 +963,8 @@ int audit_alloc_syscall(struct task_struct *tsk)
 		return 0;
 	}
 
-	if (!(context = audit_alloc_context(state))) {
+	context = audit_alloc_context(state, GFP_KERNEL);
+	if (!context) {
 		kfree(key);
 		audit_log_lost("out of memory in audit_alloc_syscall");
 		return -ENOMEM;
@@ -974,8 +976,26 @@ int audit_alloc_syscall(struct task_struct *tsk)
 	return 0;
 }
 
-static inline void audit_free_context(struct audit_context *context)
+struct audit_context *audit_alloc_local(gfp_t gfpflags)
 {
+	struct audit_context *context;
+
+	context = audit_alloc_context(AUDIT_RECORD_CONTEXT, gfpflags);
+	if (!context) {
+		audit_log_lost("out of memory in audit_alloc_local");
+		return NULL;
+	}
+	context->serial = audit_serial();
+	ktime_get_coarse_real_ts64(&context->ctime);
+	context->local = true;
+	return context;
+}
+EXPORT_SYMBOL(audit_alloc_local);
+
+void audit_free_context(struct audit_context *context)
+{
+	if (!context)
+		return;
 	audit_free_module(context);
 	audit_free_names(context);
 	unroll_tree_refs(context, NULL, 0);
@@ -986,6 +1006,7 @@ static inline void audit_free_context(struct audit_context *context)
 	audit_proctitle_free(context);
 	kfree(context);
 }
+EXPORT_SYMBOL(audit_free_context);
 
 static int audit_log_pid_context(struct audit_context *context, pid_t pid,
 				 kuid_t auid, kuid_t uid, unsigned int sessionid,
@@ -2223,7 +2244,7 @@ EXPORT_SYMBOL_GPL(__audit_inode_child);
 int auditsc_get_stamp(struct audit_context *ctx,
 		       struct timespec64 *t, unsigned int *serial)
 {
-	if (!ctx->in_syscall)
+	if (!ctx->in_syscall && !ctx->local)
 		return 0;
 	if (!ctx->serial)
 		ctx->serial = audit_serial();
-- 
2.18.4