linux-kernel - Re: [PATCH] cxl: Fix null pointer dereference in cxl_get

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Date:   Mon, 4 Dec 2023 11:43:12 +0100
From:   Frederic Barrat <fbarrat@...ux.ibm.com>
To:     Kunwu Chan <chentao@...inos.cn>, ajd@...ux.ibm.com, arnd@...db.de,
        gregkh@...uxfoundation.org, mpe@...erman.id.au,
        mrochs@...ux.vnet.ibm.com
Cc:     kunwu.chan@...mail.com, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cxl: Fix null pointer dereference in cxl_get_fd



On 04/12/2023 03:07, Kunwu Chan wrote:
> kasprintf() returns a pointer to dynamically allocated memory
> which can be NULL upon failure.
> 
> Fixes: bdecf76e319a ("cxl: Fix coredump generation when cxl_get_fd() is used")
> Signed-off-by: Kunwu Chan <chentao@...inos.cn>
> ---
>   drivers/misc/cxl/api.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
> index d85c56530863..bfd7ccd4d7e1 100644
> --- a/drivers/misc/cxl/api.c
> +++ b/drivers/misc/cxl/api.c
> @@ -419,6 +419,10 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct file_operations *fops,
>   		fops = (struct file_operations *)&afu_fops;
>   
>   	name = kasprintf(GFP_KERNEL, "cxl:%d", ctx->pe);
> +	if (!name) {
> +		put_unused_fd(fdtmp);
> +		return ERR_PTR(-ENOMEM);
> +	}


That works, but you might as well follow the existing error path:

	name = kasprintf(GFP_KERNEL, "cxl:%d", ctx->pe);
	if (!name)
		goto err_fd;

   Fred


>   	file = cxl_getfile(name, fops, ctx, flags);
>   	kfree(name);
>   	if (IS_ERR(file))