linux-kernel - Re: [PATCH -mm] ehca: avoid crash on kthread

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Message-ID: <20061225094132.GC2313@rhun.haifa.ibm.com>
Date:	Mon, 25 Dec 2006 11:41:32 +0200
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	Akinobu Mita <akinobu.mita@...il.com>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org,
	Hoang-Nam Nguyen <hnguyen@...ibm.com>,
	Christoph Raisch <raisch@...ibm.com>, akpm@...l.org
Subject: Re: [PATCH -mm] ehca: avoid crash on kthread_create() failure

On Mon, Dec 25, 2006 at 06:35:57PM +0900, Akinobu Mita wrote:
> On Mon, Dec 25, 2006 at 10:55:51AM +0200, Muli Ben-Yehuda wrote:
> > This is correct because cct is allocated via alloc_percpu, which in
> > turn calls kzalloc, which means cct->task is NULL by default, but it's
> > a little too obscure for me. How about making it explicit?
> > 
> > task = kthread_create(...)
> > if (!IS_ERR(task))
> >    cct->task = task;
> > else
> >   cct->task = NULL;
> > 
> > return cct->task;
> 
> Subject: [PATCH -mm] ehca: avoid crash on kthread_create() failure (v3)
> 
> 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@...ibm.com>
> Cc: Hoang-Nam Nguyen <hnguyen@...ibm.com>
> Cc: Christoph Raisch <raisch@...ibm.com>
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.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 +606,20 @@ 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;
> +	else
> +		cct->task = NULL;
>  
> -	return cct->task;
> +	return task;

This should be return cct->task, since we later test the return value
of create_comp_task against NULL, e.g., in comp_poll_callback and
ehca_create_comp_pool.

Cheers,
Muli
-
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