linux-kernel - Re: [patch 1/2] memstick: use after free in msb_disk

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Date:	Sun, 30 Sep 2012 00:09:14 +0200
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>
Subject: Re: [patch 1/2] memstick: use after free in msb_disk_release()

On Sat, 2012-09-29 at 10:11 +0300, Dan Carpenter wrote: 
> The original code dereferenced "msb" after freeing it.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> diff --git a/drivers/memstick/core/ms_block.c b/drivers/memstick/core/ms_block.c
> index c815fe5..a8e8915 100644
> --- a/drivers/memstick/core/ms_block.c
> +++ b/drivers/memstick/core/ms_block.c
> @@ -1983,9 +1983,9 @@ static int msb_disk_release(struct gendisk *disk)
>  			msb->usage_count--;
>  
>  		if (!msb->usage_count) {
> -			kfree(msb);
>  			disk->private_data = NULL;
>  			idr_remove(&msb_disk_idr, msb->disk_id);
> +			kfree(msb);
>  			put_disk(disk);
>  		}
>  	}

Oops, I added this bug in latest iteration, when removed support for
major.
Acked-by: Maxim Levitsky <maximlevitsly@...il.com>

Best regards,
Maxim Levitsky

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