Re: [PATCH V3 2/3] scsi: core: fix failure handling of scsi_add_host_with_dma

From: Hannes Reinecke <hare@suse.de>
To: Ming Lei <ming.lei@redhat.com>,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org
Cc: Bart Van Assche <bvanassche@acm.org>, John Garry <john.garry@huawei.com>
Subject: Re: [PATCH V3 2/3] scsi: core: fix failure handling of scsi_add_host_with_dma
Date: Mon, 31 May 2021 08:31:59 +0200	[thread overview]
Message-ID: <bb3479ee-b7ca-bfdf-92a7-b2cef90bbf59@suse.de> (raw)
In-Reply-To: <20210531050727.2353973-3-ming.lei@redhat.com>

On 5/31/21 7:07 AM, Ming Lei wrote:
> When scsi_add_host_with_dma() return failure, the caller will call
> scsi_host_put(shost) to release everything allocated for this host
> instance. So we can't free allocated stuff in scsi_add_host_with_dma(),
> otherwise double free will be caused.
> 
> Strictly speaking, these host resources allocation should have been
> moved to scsi_host_alloc(), but the allocation may need driver's
> info which can be built between calling scsi_host_alloc() and
> scsi_add_host(), so just keep the allocations in
> scsi_add_host_with_dma().
> 
> Fixes the problem by relying on host device's release handler to
> release everything.
> 
> Cc: Bart Van Assche <bvanassche@acm.org>
> Cc: John Garry <john.garry@huawei.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   drivers/scsi/hosts.c | 14 ++++++--------
>   1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index ada11e3ae577..6cbc3eb16525 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -279,23 +279,22 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
>   
>   		if (!shost->work_q) {
>   			error = -EINVAL;
> -			goto out_free_shost_data;
> +			goto out_del_dev;
>   		}
>   	}
>   
>   	error = scsi_sysfs_add_host(shost);
>   	if (error)
> -		goto out_destroy_host;
> +		goto out_del_dev;
>   
>   	scsi_proc_host_add(shost);
>   	scsi_autopm_put_host(shost);
>   	return error;
>   
> - out_destroy_host:
> -	if (shost->work_q)
> -		destroy_workqueue(shost->work_q);
> - out_free_shost_data:
> -	kfree(shost->shost_data);
> +	/*
> +	 * any host allocation in this function will be freed in
> +	 * scsi_host_dev_release, so don't free them in the failure path
> +	 */
>    out_del_dev:
>   	device_del(&shost->shost_dev);
>    out_del_gendev:
> @@ -305,7 +304,6 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
>   	pm_runtime_disable(&shost->shost_gendev);
>   	pm_runtime_set_suspended(&shost->shost_gendev);
>   	pm_runtime_put_noidle(&shost->shost_gendev);
> -	scsi_mq_destroy_tags(shost);
>    fail:
>   	return error;
>   }
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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