linux-kernel - Re: [PATCH v2] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread

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Message-Id: <5315a702-935e-4a57-a176-cf11823349b4@fnnas.com>
Date: Sat, 27 Dec 2025 09:52:45 +0800
From: "Yu Kuai" <yukuai@...as.com>
To: "Tuo Li" <islituo@...il.com>, <song@...nel.org>
Cc: <linux-raid@...r.kernel.org>, <linux-kernel@...r.kernel.org>, 
	<yukuai@...as.com>
Subject: Re: [PATCH v2] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

在 2025/12/25 21:03, Tuo Li 写道:

> The variable mddev->private is first assigned to conf and then checked:
>
>     conf = mddev->private;
>      if (!conf) ...
>
> If conf is NULL, then mddev->private is also NULL. In this case,
> null-pointer dereferences can occur when calling raid5_quiesce():
>
>    raid5_quiesce(mddev, true);
>    raid5_quiesce(mddev, false);
>
> since mddev->private is assigned to conf again in raid5_quiesce(), and conf
> is dereferenced in several places, for example:
>
>    conf->quiesce = 0;
>    wake_up(&conf->wait_for_quiescent);
>
> To fix this issue, the function should unlock mddev and return before
> invoking raid5_quiesce() when conf is NULL, following the existing pattern
> in raid5_change_consistency_policy().
>
> Fixes: fa1944bbe622 ("md/raid5: Wait sync io to finish before changing group cnt")
> Signed-off-by: Tuo Li<islituo@...il.com>
> ---
> v2:
> * Move the NULL check and early return ahead of the first call to
>    raid5_quiesce().
>    Thanks to Yu Kuai for helpful advice.
> ---
>   drivers/md/raid5.c | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)

Applied to md-6.19

-- 
Thansk,
Kuai