linux-kernel - Re: [PATCH] mpt2sas: prevent double free on error path

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Date:	Thu, 24 Jan 2013 08:51:20 +0100
From:	Bjørn Mork <bjorn@...k.no>
To:	Jörn Engel <joern@...fs.org>
Cc:	Nagalakshmi Nandigama <Nagalakshmi.Nandigama@....com>,
	Sreekanth Reddy <Sreekanth.Reddy@....com>, support@....com,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	DL-MPTFusionLinux@....com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mpt2sas: prevent double free on error path

Jörn Engel <joern@...fs.org> writes:

> diff --git a/drivers/scsi/mpt2sas/mpt2sas_scsih.c b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> index c6bdc92..43b3a98 100644
> --- a/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> +++ b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> @@ -570,6 +570,18 @@ _scsih_sas_device_find_by_handle(struct MPT2SAS_ADAPTER *ioc, u16 handle)
>  	return NULL;
>  }
>  
> +static void free_sas_device(struct kref *kref)
> +{
> +	struct _sas_device *sas_device = container_of(kref, struct _sas_device,
> +			kref);
> +	kfree(sas_device);
> +}
> +
> +static void put_sas_device(struct _sas_device *sas_device)
> +{
> +	kref_put(&sas_device->kref, free_sas_device);
> +}
> +
>  /**
>   * _scsih_sas_device_remove - remove sas_device from list.
>   * @ioc: per adapter object
> @@ -583,14 +595,19 @@ _scsih_sas_device_remove(struct MPT2SAS_ADAPTER *ioc,
>      struct _sas_device *sas_device)
>  {
>  	unsigned long flags;
> +	int was_on_list = 0;
>  
>  	if (!sas_device)
>  		return;
>  
>  	spin_lock_irqsave(&ioc->sas_device_lock, flags);
> -	list_del(&sas_device->list);
> -	kfree(sas_device);
> +	if (!list_empty(&sas_device->list)) {
> +		list_del_init(&sas_device->list);
> +		was_on_list = 1;
> +	}
>  	spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> +	if (was_on_list)
> +		put_sas_device(sas_device);
>  }
>  


How about the copy of this code in drivers/scsi/mpt3sas/mpt3sas_scsih.c?
Is that safe, or does it need fixing as well?


Bjørn
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