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SubjectRe: [PATCH -mm] ehca: avoid crash on kthread_create() failure
On Mon, Dec 25, 2006 at 05:30:23PM +0900, Akinobu Mita wrote:
> 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);
> + }

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;

Cheers,
Muli
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