[PATCH] module: kludge

[Luis Chamberlain]

Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
---
 kernel/module/main.c | 45 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 145e15f19576..a96de989532a 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -62,6 +62,16 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/module.h>
 
+#define MAX_INITMOD_CONCURRENT 50
+static atomic_t initmod_concurrent_max = ATOMIC_INIT(MAX_INITMOD_CONCURRENT);
+static DECLARE_WAIT_QUEUE_HEAD(initmod_wq);
+
+/*
+ * How much time to wait for *all*  MAX_INITMOD_CONCURRENT threads running
+ * at the same time without returning.
+ */
+#define MAX_INITMOD_ALL_BUSY_TIMEOUT 5
+
 /*
  * Mutex protects:
  * 1) List of modules (also safely readable with preempt_disable),
@@ -3015,6 +3025,30 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 	return load_module(&info, uargs, 0);
 }
 
+static int module_kread_concurrent(void)
+{
+	int err;
+
+	if (atomic_dec_if_positive(&initmod_concurrent_max) < 0) {
+		pr_warn_ratelimited("finit_module: initkmod_concurrent_max (%u) close to 0 (max_loads: %u), throttling...",
+				    atomic_read(&initmod_concurrent_max),
+				    MAX_INITMOD_CONCURRENT);
+		err = wait_event_killable_timeout(initmod_wq,
+						  atomic_dec_if_positive(&initmod_concurrent_max) >= 0,
+						  MAX_INITMOD_ALL_BUSY_TIMEOUT * HZ);
+		if (!err) {
+			pr_warn_ratelimited("finit_module: loading module cannot be processed, kernel busy with %d threads loading modules now for more than %d seconds",
+					    MAX_INITMOD_CONCURRENT, MAX_INITMOD_ALL_BUSY_TIMEOUT);
+			return -ETIME;
+		} else if (err == -ERESTARTSYS) {
+			pr_warn_ratelimited("finit_module: sigkill sent for load_module giving up");
+			return err;
+		}
+	}
+
+	return 0;
+}
+
 SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
 {
 	struct load_info info = { };
@@ -3033,6 +3067,10 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
 		      |MODULE_INIT_COMPRESSED_FILE))
 		return -EINVAL;
 
+	err = module_kread_concurrent();
+	if (err)
+		return err;
+
 	len = kernel_read_file_from_fd(fd, 0, &buf, INT_MAX, NULL,
 				       READING_MODULE);
 	if (len < 0)
@@ -3048,7 +3086,12 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
 		info.len = len;
 	}
 
-	return load_module(&info, uargs, flags);
+	err = load_module(&info, uargs, flags);
+
+	atomic_inc(&initmod_concurrent_max);
+	wake_up(&initmod_wq);
+
+	return err;
 }
 
 /* Keep in sync with MODULE_FLAGS_BUF_SIZE !!! */
-- 
2.39.2