linux-kernel - Re: 3.15-mw: Oops Workqueue: writeback bdi_writeback_workfn (flush-8:16) RIP: e030:[<ffffffff814c6bc1>] [<ffffffff814c6bc1>] kobject

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Message-ID: <195733186.20140414150611@eikelenboom.it>
Date:	Mon, 14 Apr 2014 15:06:11 +0200
From:	Sander Eikelenboom <linux@...elenboom.it>
To:	Christoph Hellwig <hch@...radead.org>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-scsi@...r.kernel.org
Subject: Re: 3.15-mw:  Oops Workqueue: writeback bdi_writeback_workfn (flush-8:16)  RIP: e030:[<ffffffff814c6bc1>]  [<ffffffff814c6bc1>] kobject_put+0x11/0x70


Monday, April 14, 2014, 1:30:15 PM, you wrote:

> On Sat, Apr 12, 2014 at 01:34:31PM +0200, Sander Eikelenboom wrote:
>> Hi,
>> 
>> I just ran into the oops belowafter some uptime.

> Classic use after free introduced by my recent changes, sorry.

> This should fix it:

Thx !

> ---
> From: Christoph Hellwig <hch@....de>
> Subject: scsi: don't reference freed command in scsi_init_sgtable

> When scsi_init_io fails we have to release our device reference, but
> we do this trying to reference the just freed command.  Add a local
> scsi_device pointer to fix this.

> Reported-by: Sander Eikelenboom <linux@...elenboom.it>
> Signed-off-by: Christoph Hellwig <hch@....de>

> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 65a123d..54eff6a 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1044,6 +1044,7 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
>   */
>  int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
>  {
> +       struct scsi_device *sdev = cmd->device;
>         struct request *rq = cmd->request;
>  
>         int error = scsi_init_sgtable(rq, &cmd->sdb, gfp_mask);
> @@ -1091,7 +1092,7 @@ err_exit:
>         scsi_release_buffers(cmd);
>         cmd->request->special = NULL;
>         scsi_put_command(cmd);
> -       put_device(&cmd->device->sdev_gendev);
> +       put_device(&sdev->sdev_gendev);
>         return error;
>  }
>  EXPORT_SYMBOL(scsi_init_io);


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