linux-kernel - Re: [PATCH] bcache: Fix NULL pointer dereference in bch_cached_dev

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Message-ID: <nqdvnxwug6dv4xkt3kmzp6eiqnrjeilyaeaoukrtime5wjrz6c@jwliy7gmljvu>
Date: Tue, 19 Dec 2023 15:08:10 +0800
From: Coly Li <colyli@...e.de>
To: Kunwu Chan <chentao@...inos.cn>
Cc: kent.overstreet@...il.com, linux-bcache@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Kunwu Chan <kunwu.chan@...mail.com>
Subject: Re: [PATCH] bcache: Fix NULL pointer dereference in
 bch_cached_dev_run

On Mon, Dec 11, 2023 at 04:25:10PM +0800, Kunwu Chan wrote:
> kasprintf() returns a pointer to dynamically allocated memory
> which can be NULL upon failure.
> 

If you check kobject_uevent_env(), you will find the NULL pointer dereference
won't happen. Sending env[1] or env[2] as NULL into kobject_uevent_env() just
results an unexpected udev event message, IMHO it is better than nothing.

> Cc: Kunwu Chan <kunwu.chan@...mail.com>
> Signed-off-by: Kunwu Chan <chentao@...inos.cn>

Why this patch is Cced to another email address of same person?

Thanks.

Coly Li

> ---
>  drivers/md/bcache/super.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 1402096b8076..40b657887d3b 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1053,6 +1053,12 @@ int bch_cached_dev_run(struct cached_dev *dc)
>  		NULL,
>  	};
>  
> +	if (!env[1] || !env[2]) {
> +		pr_err("Couldn't create bcache dev <-> fail to allocate memory\n");
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
>  	if (dc->io_disable) {
>  		pr_err("I/O disabled on cached dev %pg\n", dc->bdev);
>  		ret = -EIO;
> -- 
> 2.39.2
> 
> 

-- 
Coly Li