linux-kernel - Re: [PATCH v2] cxl: Fix null pointer dereference in cxl_get

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Message-ID: <80f1ba0d-afae-4af7-8de7-9813cb22e741@linux.ibm.com>
Date: Mon, 15 Jan 2024 12:05:22 +0100
From: Frederic Barrat <fbarrat@...ux.ibm.com>
To: Kunwu Chan <chentao@...inos.cn>, ajd@...ux.ibm.com, arnd@...db.de,
        mpe@...erman.id.au, mrochs@...ux.vnet.ibm.com
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Kunwu Chan <kunwu.chan@...mail.com>
Subject: Re: [PATCH v2] cxl: Fix null pointer dereference in cxl_get_fd



On 12/01/2024 06:49, Kunwu Chan wrote:
> kasprintf() returns a pointer to dynamically allocated memory
> which can be NULL upon failure.
> 
> Uniformly handle resource release in error paths. And when an
> error occurs, an error pointer should be returned.
> 
> Fixes: bdecf76e319a ("cxl: Fix coredump generation when cxl_get_fd() is used")
> Signed-off-by: Kunwu Chan <chentao@...inos.cn>
> Cc: Kunwu Chan <kunwu.chan@...mail.com>
> Suggested-by: Frederic Barrat <fbarrat@...ux.ibm.com>
> ---

Thanks!
Acked-by: Frederic Barrat <fbarrat@...ux.ibm.com>

   Fred


> v2: Deal with error path
> ---
>   drivers/misc/cxl/api.c | 18 ++++++++++++++----
>   1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
> index d85c56530863..b49bc3d29fc0 100644
> --- a/drivers/misc/cxl/api.c
> +++ b/drivers/misc/cxl/api.c
> @@ -389,19 +389,22 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct file_operations *fops,
>   			int *fd)
>   {
>   	struct file *file;
> -	int rc, flags, fdtmp;
> +	int rc = 0, flags, fdtmp;
>   	char *name = NULL;
>   
>   	/* only allow one per context */
> -	if (ctx->mapping)
> -		return ERR_PTR(-EEXIST);
> +	if (ctx->mapping) {
> +		rc = -EEXIST;
> +		goto err;
> +	}
>   
>   	flags = O_RDWR | O_CLOEXEC;
>   
>   	/* This code is similar to anon_inode_getfd() */
>   	rc = get_unused_fd_flags(flags);
>   	if (rc < 0)
> -		return ERR_PTR(rc);
> +		goto err;
> +
>   	fdtmp = rc;
>   
>   	/*
> @@ -419,6 +422,10 @@ 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) {
> +		rc = -ENOMEM;
> +		goto err_fd;
> +	}
>   	file = cxl_getfile(name, fops, ctx, flags);
>   	kfree(name);
>   	if (IS_ERR(file))
> @@ -430,6 +437,9 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct file_operations *fops,
>   
>   err_fd:
>   	put_unused_fd(fdtmp);
> +err:
> +	if (rc < 0)
> +		return ERR_PTR(rc);
>   	return NULL;
>   }
>   EXPORT_SYMBOL_GPL(cxl_get_fd);