linux-kernel - Re: [PATCH] scsi: avoid use of reclaimed reference

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Message-ID: <52836B53.4080204@acm.org>
Date:	Wed, 13 Nov 2013 13:06:43 +0100
From:	Bart Van Assche <bvanassche@....org>
To:	David Decotigny <decot@...glers.com>, linux-scsi@...r.kernel.org
CC:	"James E.J. Bottomley" <JBottomley@...allels.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: avoid use of reclaimed reference

On 11/13/13 02:10, David Decotigny wrote:
> This patch avoids to use an object after it was potentially reclaimed
> by scsi_device_put().
>
> Signed-off-by: David Decotigny <decot@...glers.com>
> ---
>   drivers/scsi/scsi_scan.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 307a811..16e4a44 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -1498,12 +1498,14 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
>    out_err:
>   	kfree(lun_data);
>    out:
> -	scsi_device_put(sdev);
> -	if (scsi_device_created(sdev))
> +	if (scsi_device_created(sdev)) {
>   		/*
>   		 * the sdev we used didn't appear in the report luns scan
>   		 */
>   		__scsi_remove_device(sdev);
> +	}
> +
> +	scsi_device_put(sdev);
>   	return ret;
>   }

It would help if you could explain why you started looking at this code. 
Is the above patch something you came up with after having analyzed the 
SCSI mid-layer source code or perhaps as the result of a test that 
failed ? If so, which test was it that failed ?

Thanks,

Bart.

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