linux-kernel - Re: [PATCH v2 1/1] cxl/core: Fix initialization of mbox_cmd.size

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Date: Tue, 2 Apr 2024 15:38:58 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Kwangjin Ko <kwangjin.ko@...com>
CC: <dave@...olabs.net>, <dave.jiang@...el.com>, <alison.schofield@...el.com>,
	<vishal.l.verma@...el.com>, <ira.weiny@...el.com>,
	<dan.j.williams@...el.com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <kernel_team@...ynix.com>
Subject: Re: [PATCH v2 1/1] cxl/core: Fix initialization of
 mbox_cmd.size_out in get event

On Tue, 2 Apr 2024 17:14:03 +0900
Kwangjin Ko <kwangjin.ko@...com> wrote:

> Since mbox_cmd.size_out is overwritten with the actual output size in
> the function below, it needs to be initialized every time.
> 
> cxl_internal_send_cmd -> __cxl_pci_mbox_send_cmd
> 
> Problem scenario:
> 
> 1) The size_out variable is initially set to the size of the mailbox.
> 2) Read an event.
>    - size_out is set to 160 bytes(header 32B + one event 128B).
>    - Two event are created while reading.
> 3) Read the new *two* events.
>    - size_out is still set to 160 bytes.
>    - Although the value of out_len is 288 bytes, only 160 bytes are
>      copied from the mailbox register to the local variable.
>    - record_count is set to 2.
>    - Accessing records[1] will result in reading incorrect data.
> 
> Signed-off-by: Kwangjin Ko <kwangjin.ko@...com>

Looks correct to me.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  drivers/cxl/core/mbox.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 9adda4795eb7..a38531a055c8 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -958,13 +958,14 @@ static void cxl_mem_get_records_log(struct cxl_memdev_state *mds,
>  		.payload_in = &log_type,
>  		.size_in = sizeof(log_type),
>  		.payload_out = payload,
> -		.size_out = mds->payload_size,
>  		.min_out = struct_size(payload, records, 0),
>  	};
>  
>  	do {
>  		int rc, i;
>  
> +		mbox_cmd.size_out = mds->payload_size;
> +
>  		rc = cxl_internal_send_cmd(mds, &mbox_cmd);
>  		if (rc) {
>  			dev_err_ratelimited(dev,