From d2849f27bc03b66f81f31aa571c8db997bad8fcb Mon Sep 17 00:00:00 2001
From: Adrian Chadd <adrian@FreeBSD.org>
Date: Thu, 15 Sep 2011 08:42:06 +0000
Subject: [PATCH] Ensure that ta_pending doesn't overflow u_short by capping
 its value at USHRT_MAX.

If it overflows before the taskqueue can run, the task will be
re-added to the taskqueue and cause a loop in the task list.

Reported by:	Arnaud Lacombe <lacombar@gmail.com>
Submitted by:	Ryan Stone <rysto32@gmail.com>
Reviewed by:	jhb
Approved by:	re (kib)
MFC after:	1 day
---
 share/man/man9/taskqueue.9 | 2 +-
 sys/kern/subr_taskqueue.c  | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/share/man/man9/taskqueue.9 b/share/man/man9/taskqueue.9
index f45a149e189b..40d64af39639 100644
--- a/share/man/man9/taskqueue.9
+++ b/share/man/man9/taskqueue.9
@@ -133,7 +133,7 @@ If the task's
 .Va ta_pending
 field is non-zero,
 then it is simply incremented to reflect the number of times the task
-was enqueued.
+was enqueued, up to a cap of USHRT_MAX.
 Otherwise,
 the task is added to the list before the first task which has a lower
 .Va ta_priority
diff --git a/sys/kern/subr_taskqueue.c b/sys/kern/subr_taskqueue.c
index 4c4589901557..31ea52d1d876 100644
--- a/sys/kern/subr_taskqueue.c
+++ b/sys/kern/subr_taskqueue.c
@@ -33,6 +33,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/interrupt.h>
 #include <sys/kernel.h>
 #include <sys/kthread.h>
+#include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/mutex.h>
@@ -173,7 +174,8 @@ taskqueue_enqueue_locked(struct taskqueue *queue, struct task *task)
 	 * Count multiple enqueues.
 	 */
 	if (task->ta_pending) {
-		task->ta_pending++;
+		if (task->ta_pending < USHRT_MAX)
+			task->ta_pending++;
 		return (0);
 	}