linux-kernel - Re: [PATCH v2 0/5] md: fix uaf for sync

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Date:   Wed, 15 Mar 2023 09:30:26 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     Yu Kuai <yukuai1@...weicloud.com>, agk@...hat.com,
        snitzer@...nel.org, song@...nel.org, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v2 0/5] md: fix uaf for sync_thread

Dear Logan,


Am 15.03.23 um 07:18 schrieb Yu Kuai:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Changes in v2:
>   - fix a compile error for for md-cluster in patch 2
>   - replace spin_lock/unlock with spin_lock/unlock_irq in patch 5
>   - don't wake up inside the new lock in md wakeup_thread in patch 5
> 
> Our test reports a uaf for 'mddev->sync_thread':
> 
> T1                      T2
> md_start_sync
>   md_register_thread
> 			raid1d
> 			 md_check_recovery
> 			  md_reap_sync_thread
> 			   md_unregister_thread
> 			    kfree
> 
>   md_wakeup_thread
>    wake_up
>    ->sync_thread was freed
> 
> Currently, a global spinlock 'pers_lock' is borrowed to protect
> 'mddev->thread', this problem can be fixed likewise, however, there might
> be similar problem for other md_thread, and I really don't like the idea to
> borrow a global lock.
> 
> This patchset do some refactor, and then use a disk level spinlock to
> protect md_thread in relevant apis.
> 
> I tested this pathset with mdadm tests, and there are no new regression,
> by the way, following test will failed with or without this patchset:
> 
> 01raid6integ
> 04r1update
> 05r6tor0
> 10ddf-create
> 10ddf-fail-spare
> 10ddf-fail-stop-readd
> 10ddf-geometry

As you improved the tests in the past, can you confirm, these failed on 
your test systems too and are fixed now?

[…]


Kind regards,

Paul