audit: use current whenever possible

There are many places, notably audit_log_task_info() and audit_log_exit(), that take task_struct pointers but in reality they are always working on the current task. This patch eliminates the task_struct arguments and uses current directly which allows a number of cleanups as well. Acked-by: Richard Guy Briggs <[email protected]> Signed-off-by: Paul Moore <[email protected]>
jbg · Nov 26, 2018 · 2a1fe21 · 2a1fe21
1 parent d0a3f18
commit 2a1fe21
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Showing 6 changed files with 90 additions and 98 deletions.
diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c
@@ -61,20 +61,19 @@ static void tty_audit_log(const char *description, dev_t dev,
 			  unsigned char *data, size_t size)
 {
 	struct audit_buffer *ab;
-	struct task_struct *tsk = current;
-	pid_t pid = task_pid_nr(tsk);
-	uid_t uid = from_kuid(&init_user_ns, task_uid(tsk));
-	uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(tsk));
-	unsigned int sessionid = audit_get_sessionid(tsk);
+	pid_t pid = task_pid_nr(current);
+	uid_t uid = from_kuid(&init_user_ns, task_uid(current));
+	uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current));
+	unsigned int sessionid = audit_get_sessionid(current);
 
 	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
 	if (ab) {
-		char name[sizeof(tsk->comm)];
+		char name[sizeof(current->comm)];
 
 		audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
 				 " minor=%d comm=", description, pid, uid,
 				 loginuid, sessionid, MAJOR(dev), MINOR(dev));
-		get_task_comm(name, tsk);
+		get_task_comm(name, current);
 		audit_log_untrustedstring(ab, name);
 		audit_log_format(ab, " data=");
 		audit_log_n_hex(ab, data, size);

diff --git a/include/linux/audit.h b/include/linux/audit.h
@@ -151,8 +151,7 @@ extern void		    audit_log_link_denied(const char *operation);
 extern void		    audit_log_lost(const char *message);
 
 extern int audit_log_task_context(struct audit_buffer *ab);
-extern void audit_log_task_info(struct audit_buffer *ab,
-				struct task_struct *tsk);
+extern void audit_log_task_info(struct audit_buffer *ab);
 
 extern int		    audit_update_lsm_rules(void);
 
@@ -200,8 +199,7 @@ static inline int audit_log_task_context(struct audit_buffer *ab)
 {
 	return 0;
 }
-static inline void audit_log_task_info(struct audit_buffer *ab,
-				       struct task_struct *tsk)
+static inline void audit_log_task_info(struct audit_buffer *ab)
 { }
 #define audit_enabled AUDIT_OFF
 #endif /* CONFIG_AUDIT */

diff --git a/kernel/audit.c b/kernel/audit.c
@@ -1096,10 +1096,11 @@ static void audit_log_feature_change(int which, u32 old_feature, u32 new_feature
 
 	if (audit_enabled == AUDIT_OFF)
 		return;
+
 	ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_FEATURE_CHANGE);
 	if (!ab)
 		return;
-	audit_log_task_info(ab, current);
+	audit_log_task_info(ab);
 	audit_log_format(ab, " feature=%s old=%u new=%u old_lock=%u new_lock=%u res=%d",
 			 audit_feature_names[which], !!old_feature, !!new_feature,
 			 !!old_lock, !!new_lock, res);
@@ -2246,15 +2247,15 @@ void audit_log_d_path_exe(struct audit_buffer *ab,
 	audit_log_format(ab, " exe=(null)");
 }
 
-struct tty_struct *audit_get_tty(struct task_struct *tsk)
+struct tty_struct *audit_get_tty(void)
 {
 	struct tty_struct *tty = NULL;
 	unsigned long flags;
 
-	spin_lock_irqsave(&tsk->sighand->siglock, flags);
-	if (tsk->signal)
-		tty = tty_kref_get(tsk->signal->tty);
-	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
+	spin_lock_irqsave(&current->sighand->siglock, flags);
+	if (current->signal)
+		tty = tty_kref_get(current->signal->tty);
+	spin_unlock_irqrestore(&current->sighand->siglock, flags);
 	return tty;
 }
 
@@ -2263,25 +2264,24 @@ void audit_put_tty(struct tty_struct *tty)
 	tty_kref_put(tty);
 }
 
-void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
+void audit_log_task_info(struct audit_buffer *ab)
 {
 	const struct cred *cred;
-	char comm[sizeof(tsk->comm)];
+	char comm[sizeof(current->comm)];
 	struct tty_struct *tty;
 
 	if (!ab)
 		return;
 
-	/* tsk == current */
 	cred = current_cred();
-	tty = audit_get_tty(tsk);
+	tty = audit_get_tty();
 	audit_log_format(ab,
 			 " ppid=%d pid=%d auid=%u uid=%u gid=%u"
 			 " euid=%u suid=%u fsuid=%u"
 			 " egid=%u sgid=%u fsgid=%u tty=%s ses=%u",
-			 task_ppid_nr(tsk),
-			 task_tgid_nr(tsk),
-			 from_kuid(&init_user_ns, audit_get_loginuid(tsk)),
+			 task_ppid_nr(current),
+			 task_tgid_nr(current),
+			 from_kuid(&init_user_ns, audit_get_loginuid(current)),
 			 from_kuid(&init_user_ns, cred->uid),
 			 from_kgid(&init_user_ns, cred->gid),
 			 from_kuid(&init_user_ns, cred->euid),
@@ -2291,11 +2291,11 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
 			 from_kgid(&init_user_ns, cred->sgid),
 			 from_kgid(&init_user_ns, cred->fsgid),
 			 tty ? tty_name(tty) : "(none)",
-			 audit_get_sessionid(tsk));
+			 audit_get_sessionid(current));
 	audit_put_tty(tty);
 	audit_log_format(ab, " comm=");
-	audit_log_untrustedstring(ab, get_task_comm(comm, tsk));
-	audit_log_d_path_exe(ab, tsk->mm);
+	audit_log_untrustedstring(ab, get_task_comm(comm, current));
+	audit_log_d_path_exe(ab, current->mm);
 	audit_log_task_context(ab);
 }
 EXPORT_SYMBOL(audit_log_task_info);
@@ -2316,7 +2316,7 @@ void audit_log_link_denied(const char *operation)
 	if (!ab)
 		return;
 	audit_log_format(ab, "op=%s", operation);
-	audit_log_task_info(ab, current);
+	audit_log_task_info(ab);
 	audit_log_format(ab, " res=0");
 	audit_log_end(ab);
 }

diff --git a/kernel/audit.h b/kernel/audit.h
@@ -264,7 +264,7 @@ extern struct audit_entry *audit_dupe_rule(struct audit_krule *old);
 extern void audit_log_d_path_exe(struct audit_buffer *ab,
 				 struct mm_struct *mm);
 
-extern struct tty_struct *audit_get_tty(struct task_struct *tsk);
+extern struct tty_struct *audit_get_tty(void);
 extern void audit_put_tty(struct tty_struct *tty);
 
 /* audit watch functions */

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
@@ -830,44 +830,6 @@ void audit_filter_inodes(struct task_struct *tsk, struct audit_context *ctx)
 	rcu_read_unlock();
 }
 
-/* Transfer the audit context pointer to the caller, clearing it in the tsk's struct */
-static inline struct audit_context *audit_take_context(struct task_struct *tsk,
-						      int return_valid,
-						      long return_code)
-{
-	struct audit_context *context = tsk->audit_context;
-
-	if (!context)
-		return NULL;
-	context->return_valid = return_valid;
-
-	/*
-	 * we need to fix up the return code in the audit logs if the actual
-	 * return codes are later going to be fixed up by the arch specific
-	 * signal handlers
-	 *
-	 * This is actually a test for:
-	 * (rc == ERESTARTSYS ) || (rc == ERESTARTNOINTR) ||
-	 * (rc == ERESTARTNOHAND) || (rc == ERESTART_RESTARTBLOCK)
-	 *
-	 * but is faster than a bunch of ||
-	 */
-	if (unlikely(return_code <= -ERESTARTSYS) &&
-	    (return_code >= -ERESTART_RESTARTBLOCK) &&
-	    (return_code != -ENOIOCTLCMD))
-		context->return_code = -EINTR;
-	else
-		context->return_code  = return_code;
-
-	if (context->in_syscall && !context->dummy) {
-		audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_EXIT]);
-		audit_filter_inodes(tsk, context);
-	}
-
-	audit_set_context(tsk, NULL);
-	return context;
-}
-
 static inline void audit_proctitle_free(struct audit_context *context)
 {
 	kfree(context->proctitle.value);
@@ -1296,15 +1258,18 @@ static inline int audit_proctitle_rtrim(char *proctitle, int len)
 	return len;
 }
 
-static void audit_log_proctitle(struct task_struct *tsk,
-			 struct audit_context *context)
+static void audit_log_proctitle(void)
 {
 	int res;
 	char *buf;
 	char *msg = "(null)";
 	int len = strlen(msg);
+	struct audit_context *context = audit_context();
 	struct audit_buffer *ab;
 
+	if (!context || context->dummy)
+		return;
+
 	ab = audit_log_start(context, GFP_KERNEL, AUDIT_PROCTITLE);
 	if (!ab)
 		return;	/* audit_panic or being filtered */
@@ -1317,7 +1282,7 @@ static void audit_log_proctitle(struct task_struct *tsk,
 		if (!buf)
 			goto out;
 		/* Historically called this from procfs naming */
-		res = get_cmdline(tsk, buf, MAX_PROCTITLE_AUDIT_LEN);
+		res = get_cmdline(current, buf, MAX_PROCTITLE_AUDIT_LEN);
 		if (res == 0) {
 			kfree(buf);
 			goto out;
@@ -1337,15 +1302,15 @@ static void audit_log_proctitle(struct task_struct *tsk,
 	audit_log_end(ab);
 }
 
-static void audit_log_exit(struct audit_context *context, struct task_struct *tsk)
+static void audit_log_exit(void)
 {
 	int i, call_panic = 0;
+	struct audit_context *context = audit_context();
 	struct audit_buffer *ab;
 	struct audit_aux_data *aux;
 	struct audit_names *n;
 
-	/* tsk == current */
-	context->personality = tsk->personality;
+	context->personality = current->personality;
 
 	ab = audit_log_start(context, GFP_KERNEL, AUDIT_SYSCALL);
 	if (!ab)
@@ -1367,7 +1332,7 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
 			 context->argv[3],
 			 context->name_count);
 
-	audit_log_task_info(ab, tsk);
+	audit_log_task_info(ab);
 	audit_log_key(ab, context->filterkey);
 	audit_log_end(ab);
 
@@ -1456,7 +1421,7 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
 		audit_log_name(context, n, NULL, i++, &call_panic);
 	}
 
-	audit_log_proctitle(tsk, context);
+	audit_log_proctitle();
 
 	/* Send end of event record to help user space know we are finished */
 	ab = audit_log_start(context, GFP_KERNEL, AUDIT_EOE);
@@ -1474,22 +1439,31 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
  */
 void __audit_free(struct task_struct *tsk)
 {
-	struct audit_context *context;
+	struct audit_context *context = tsk->audit_context;
 
-	context = audit_take_context(tsk, 0, 0);
 	if (!context)
 		return;
 
-	/* Check for system calls that do not go through the exit
-	 * function (e.g., exit_group), then free context block.
-	 * We use GFP_ATOMIC here because we might be doing this
-	 * in the context of the idle thread */
-	/* that can happen only if we are called from do_exit() */
-	if (context->in_syscall && context->current_state == AUDIT_RECORD_CONTEXT)
-		audit_log_exit(context, tsk);
+	/* We are called either by do_exit() or the fork() error handling code;
+	 * in the former case tsk == current and in the latter tsk is a
+	 * random task_struct that doesn't doesn't have any meaningful data we
+	 * need to log via audit_log_exit().
+	 */
+	if (tsk == current && !context->dummy && context->in_syscall) {
+		context->return_valid = 0;
+		context->return_code = 0;
+
+		audit_filter_syscall(tsk, context,
+				     &audit_filter_list[AUDIT_FILTER_EXIT]);
+		audit_filter_inodes(tsk, context);
+		if (context->current_state == AUDIT_RECORD_CONTEXT)
+			audit_log_exit();
+	}
+
 	if (!list_empty(&context->killed_trees))
 		audit_kill_trees(&context->killed_trees);
 
+	audit_set_context(tsk, NULL);
 	audit_free_context(context);
 }
 
@@ -1559,17 +1533,40 @@ void __audit_syscall_exit(int success, long return_code)
 {
 	struct audit_context *context;
 
-	if (success)
-		success = AUDITSC_SUCCESS;
-	else
-		success = AUDITSC_FAILURE;
-
-	context = audit_take_context(current, success, return_code);
+	context = audit_context();
 	if (!context)
 		return;
 
-	if (context->in_syscall && context->current_state == AUDIT_RECORD_CONTEXT)
-		audit_log_exit(context, current);
+	if (!context->dummy && context->in_syscall) {
+		if (success)
+			context->return_valid = AUDITSC_SUCCESS;
+		else
+			context->return_valid = AUDITSC_FAILURE;
+
+		/*
+		 * we need to fix up the return code in the audit logs if the
+		 * actual return codes are later going to be fixed up by the
+		 * arch specific signal handlers
+		 *
+		 * This is actually a test for:
+		 * (rc == ERESTARTSYS ) || (rc == ERESTARTNOINTR) ||
+		 * (rc == ERESTARTNOHAND) || (rc == ERESTART_RESTARTBLOCK)
+		 *
+		 * but is faster than a bunch of ||
+		 */
+		if (unlikely(return_code <= -ERESTARTSYS) &&
+		    (return_code >= -ERESTART_RESTARTBLOCK) &&
+		    (return_code != -ENOIOCTLCMD))
+			context->return_code = -EINTR;
+		else
+			context->return_code  = return_code;
+
+		audit_filter_syscall(current, context,
+				     &audit_filter_list[AUDIT_FILTER_EXIT]);
+		audit_filter_inodes(current, context);
+		if (context->current_state == AUDIT_RECORD_CONTEXT)
+			audit_log_exit();
+	}
 
 	context->in_syscall = 0;
 	context->prio = context->state == AUDIT_RECORD_CONTEXT ? ~0ULL : 0;
@@ -1591,7 +1588,6 @@ void __audit_syscall_exit(int success, long return_code)
 		kfree(context->filterkey);
 		context->filterkey = NULL;
 	}
-	audit_set_context(current, context);
 }
 
 static inline void handle_one(const struct inode *inode)
@@ -2025,7 +2021,7 @@ static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t kloginuid,
 	uid = from_kuid(&init_user_ns, task_uid(current));
 	oldloginuid = from_kuid(&init_user_ns, koldloginuid);
 	loginuid = from_kuid(&init_user_ns, kloginuid),
-	tty = audit_get_tty(current);
+	tty = audit_get_tty();
 
 	audit_log_format(ab, "pid=%d uid=%u", task_tgid_nr(current), uid);
 	audit_log_task_context(ab);
@@ -2046,7 +2042,6 @@ static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t kloginuid,
  */
 int audit_set_loginuid(kuid_t loginuid)
 {
-	struct task_struct *task = current;
 	unsigned int oldsessionid, sessionid = AUDIT_SID_UNSET;
 	kuid_t oldloginuid;
 	int rc;
@@ -2065,8 +2060,8 @@ int audit_set_loginuid(kuid_t loginuid)
 			sessionid = (unsigned int)atomic_inc_return(&session_id);
 	}
 
-	task->sessionid = sessionid;
-	task->loginuid = loginuid;
+	current->sessionid = sessionid;
+	current->loginuid = loginuid;
 out:
 	audit_log_set_loginuid(oldloginuid, loginuid, oldsessionid, sessionid, rc);
 	return rc;

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
@@ -336,7 +336,7 @@ void ima_audit_measurement(struct integrity_iint_cache *iint,
 	audit_log_untrustedstring(ab, filename);
 	audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);
 
-	audit_log_task_info(ab, current);
+	audit_log_task_info(ab);
 	audit_log_end(ab);
 
 	iint->flags |= IMA_AUDITED;