Re: [PATCH] ibmasm driver: don't use previously freed pointer

[Greg KH <greg@kroah.com>]

On Fri, Feb 03, 2006 at 02:26:38PM -0800, Max Asbock wrote:
> ibmasm driver:
> Fix the command_put() function which uses a pointer for a spinlock that
> can be freed before dereferencing it.
> 
> Signed-off-by: Max Asbock masbock@us.ibm.com
> 
> ---
> 
> diff -burpN linux-2.6.16-rc1/drivers/misc/ibmasm/ibmasm.h linux-2.6.16-rc1.ibmasm/drivers/misc/ibmasm/ibmasm.h
> --- linux-2.6.16-rc1/drivers/misc/ibmasm/ibmasm.h	2006-02-01 11:50:01.000000000 -0800
> +++ linux-2.6.16-rc1.ibmasm/drivers/misc/ibmasm/ibmasm.h	2006-02-03 13:57:42.000000000 -0800
> @@ -101,10 +101,11 @@ struct command {
>  static inline void command_put(struct command *cmd)
>  {
>  	unsigned long flags;
> +	spinlock_t *lock = cmd->lock;
>  
> -	spin_lock_irqsave(cmd->lock, flags);
> +	spin_lock_irqsave(lock, flags);
>          kobject_put(&cmd->kobj);
> -	spin_unlock_irqrestore(cmd->lock, flags);
> +	spin_unlock_irqrestore(lock, flags);
>  }

If this patch is true, doesn't the spinlock the pointer is pointing out
still get deleted?

Yes you save a pointer off, but it looks like the problem is still
present.

Or am I missing something?

thanks,

greg k-h