Re: [PATCH -mm] ehca: avoid crash on kthread_create() failure

[Akinobu Mita <akinobu.mita@gmail.com>]

On Mon, Dec 25, 2006 at 05:12:57PM +0900, Akinobu Mita wrote:
> Index: 2.6-mm/drivers/infiniband/hw/ehca/ehca_irq.c
> ===================================================================
> --- 2.6-mm.orig/drivers/infiniband/hw/ehca/ehca_irq.c
> +++ 2.6-mm/drivers/infiniband/hw/ehca/ehca_irq.c
> @@ -606,13 +606,16 @@ static int comp_task(void *__cct)
>  static struct task_struct *create_comp_task(struct ehca_comp_pool *pool,
>  					    int cpu)
>  {
> +	struct task_struct *task;
>  	struct ehca_cpu_comp_task *cct;
>  
>  	cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
>  	spin_lock_init(&cct->task_lock);
>  	INIT_LIST_HEAD(&cct->cq_list);
>  	init_waitqueue_head(&cct->wait_queue);
> -	cct->task = kthread_create(comp_task, cct, "ehca_comp/%d", cpu);
> +	task = kthread_create(comp_task, cct, "ehca_comp/%d", cpu);
> +	if (!IS_ERR(task))
> +		cct->task = task;
>  
>  	return cct->task;
>  }

This patch is wrong. It changes to make create_comp_task() return NULL
on failure.

(BTW, all these ehca fixes are not compile tested due to luck of
cross comile environment)

Subject: [PATCH -mm] ehca: avoid crash on kthread_create() failure (v2)

This patch disallows invalid task_struct pointer returned by
kthread_create() to be written to percpu data to avoid crash.

Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Hoang-Nam Nguyen <hnguyen@de.ibm.com>
Cc: Christoph Raisch <raisch@de.ibm.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>

---
 drivers/infiniband/hw/ehca/ehca_irq.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Index: 2.6-mm/drivers/infiniband/hw/ehca/ehca_irq.c
===================================================================
--- 2.6-mm.orig/drivers/infiniband/hw/ehca/ehca_irq.c
+++ 2.6-mm/drivers/infiniband/hw/ehca/ehca_irq.c
@@ -606,15 +606,18 @@ static int comp_task(void *__cct)
 static struct task_struct *create_comp_task(struct ehca_comp_pool *pool,
 					    int cpu)
 {
+	struct task_struct *task;
 	struct ehca_cpu_comp_task *cct;
 
 	cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
 	spin_lock_init(&cct->task_lock);
 	INIT_LIST_HEAD(&cct->cq_list);
 	init_waitqueue_head(&cct->wait_queue);
-	cct->task = kthread_create(comp_task, cct, "ehca_comp/%d", cpu);
+	task = kthread_create(comp_task, cct, "ehca_comp/%d", cpu);
+	if (!IS_ERR(task))
+		cct->task = task;
 
-	return cct->task;
+	return task;
 }
 
 static void destroy_comp_task(struct ehca_comp_pool *pool,
@@ -684,8 +687,10 @@ static int comp_pool_callback(struct not
 	case CPU_UP_CANCELED:
 		ehca_gen_dbg("CPU: %x (CPU_CANCELED)", cpu);
 		cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
-		kthread_bind(cct->task, any_online_cpu(cpu_online_map));
-		destroy_comp_task(pool, cpu);
+		if (cct->task) {
+			kthread_bind(cct->task, any_online_cpu(cpu_online_map));
+			destroy_comp_task(pool, cpu);
+		}
 		break;
 	case CPU_ONLINE:
 		ehca_gen_dbg("CPU: %x (CPU_ONLINE)", cpu);