Re: [PATCH] block: Avoid accessing an already freed kobject in delete_partition

From: Rajat Asthana <thisisrast7@gmail.com>
To: Christoph Hellwig <hch@infradead.org>,
	Rajat Asthana <rajatasthana4@gmail.com>
Cc: axboe@kernel.dk, damien.lemoal@wdc.com, jack@suse.cz,
	rafael@kernel.org,
	syzbot+7d6c5587ec9cff5be65c@syzkaller.appspotmail.com,
	linux-kernel@vger.kernel.org, ming.lei@redhat.com,
	linux-block@vger.kernel.org, hare@suse.de,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH] block: Avoid accessing an already freed kobject in delete_partition
Date: Tue, 6 Jul 2021 06:31:11 +0530	[thread overview]
Message-ID: <0c623d71-6d99-2e0d-4d8b-63a1ff814dc1@gmail.com> (raw)
In-Reply-To: <YN/1DOeSA5ODf1AV@infradead.org>

On 03/07/21 10:56 am, Christoph Hellwig wrote:
> This should be fixed properly by:
> 
> "block: check disk exist before trying to add partition"

Hi Christoph, thanks a lot for suggesting this fix. I have been
working on implementing this and have tried the following:
- I checked if the the kobject of device structure embedded in
   gendisk structure is not NULL, to add the partition.
   This didn't work.

- Then I checked the if kobject of the block_device struct (part0)
   embedded in the gendisk struct is not NULL, to add the partition.
   This also didn't work.

- Then I checked the i_state of the bd_inode field of block_device
   struct embedded in the gendisk struct. I checked if the I_FREEING or
   I_WILL_FREE fields are not set. The reason behind doing this was
   to confirm that we only create partition on the disks which are not
   being freed.

Am I going in the right direction? Can you point me to the correct
direction if I am not?

thanks
-- Rajat