Hi,

On Sun, Feb 21, 2021 at 06:25:51PM -0800, Randy Dunlap wrote:

Hi--

On 2/21/21 7:49 AM, John Wood wrote:

quoted

+/**
+ * print_fork_attack_running() - Warn about a fork brute force attack.
+ */
+static inline void print_fork_attack_running(void)
+{
+	pr_warn("Fork brute force attack detected [%s]\n", current->comm);
+}

Do these pr_warn() calls need to be rate-limited so that they don't
flood the kernel log?

I think it is not necessary since when a brute force attack through the fork
system call is detected, a fork warning appears only once. Then, all the
offending tasks involved in the attack are killed. But if the parent try to run
again the same app already killed, a new crash will trigger a brute force attack
through the execve system call, then this parent is killed, and a new warning
message appears. Now, the parent and childs are killed, the attacks are
mitigated and only a few messages (one or two) have been shown in the kernel
log.

Thanks,
John Wood

quoted

+/**
+ * print_exec_attack_running() - Warn about an exec brute force attack.
+ * @stats: Statistical data shared by all the fork hierarchy processes.
+ *
+ * The statistical data shared by all the fork hierarchy processes cannot be
+ * NULL.
+ *
+ * Before showing the process name it is mandatory to find a process that holds
+ * a pointer to the exec statistics.
+ *
+ * Context: Must be called with tasklist_lock and brute_stats_ptr_lock held.
+ */
+static void print_exec_attack_running(const struct brute_stats *stats)
+{
+	struct task_struct *p;
+	struct brute_stats **p_stats;
+	bool found = false;
+
+	for_each_process(p) {
+		p_stats = brute_stats_ptr(p);
+		if (*p_stats == stats) {
+			found = true;
+			break;
+		}
 	}
+
+	if (WARN(!found, "No exec process\n"))
+		return;
+
+	pr_warn("Exec brute force attack detected [%s]\n", p->comm);
+}

thanks.
--
~Randy