linux-kernel - Re: [PATCH] md: fix potential NULL pointer dereference in md_super

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Message-ID: <daf88fa3-f87e-a0c7-b93c-a4d150be8afc@huaweicloud.com>
Date: Fri, 23 May 2025 17:59:09 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Ye Chey <yechey@...sast.com>, song@...nel.org
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] md: fix potential NULL pointer dereference in
 md_super_write

Hi,

在 2025/05/23 17:35, Ye Chey 写道:
> The bio_alloc_bioset() call in md_super_write() could fail under memory
> pressure and return NULL. Add a check to handle this case gracefully by
> returning early, preventing a potential NULL pointer dereference.

NAK, if you read the comments of bio_alloc_bioset(), you'll know there
are cases bio_alloc_bioset() will never return NULL.

Thanks,
Kuai

> 
> Signed-off-by: Ye Chey <yechey@...sast.com>
> ---
>   drivers/md/md.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9daa78c5f..a0e2d90d4 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1002,6 +1002,8 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
>   			      REQ_OP_WRITE | REQ_SYNC | REQ_IDLE | REQ_META
>   				  | REQ_PREFLUSH | REQ_FUA,
>   			      GFP_NOIO, &mddev->sync_set);
> +	if (!bio)
> +		return;
>   
>   	atomic_inc(&rdev->nr_pending);
>   
>