linux-kernel - Re: [PATCH v7 5/6] nbd: partition nbd_read_stat() into nbd_read_reply() and nbd_handle

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Message-ID: <YUL5lm2h+f9lG8LD@T590>
Date:   Thu, 16 Sep 2021 16:00:22 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     josef@...icpanda.com, axboe@...nel.dk, hch@...radead.org,
        linux-block@...r.kernel.org, nbd@...er.debian.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com
Subject: Re: [PATCH v7 5/6] nbd: partition nbd_read_stat() into
 nbd_read_reply() and nbd_handle_reply()

On Wed, Sep 15, 2021 at 05:20:09PM +0800, Yu Kuai wrote:
> Prepare to fix uaf in nbd_read_stat(), no functional changes.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>  drivers/block/nbd.c | 76 +++++++++++++++++++++++++++------------------
>  1 file changed, 45 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 22c91d8901f6..9a7bbf8ebe74 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -694,38 +694,45 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
>  	return 0;
>  }
>  
> -/* NULL returned = something went wrong, inform userspace */
> -static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
> +static int nbd_read_reply(struct nbd_device *nbd, int index,
> +			  struct nbd_reply *reply)
>  {
> -	struct nbd_config *config = nbd->config;
> -	int result;
> -	struct nbd_reply reply;
> -	struct nbd_cmd *cmd;
> -	struct request *req = NULL;
> -	u64 handle;
> -	u16 hwq;
> -	u32 tag;
> -	struct kvec iov = {.iov_base = &reply, .iov_len = sizeof(reply)};
> +	struct kvec iov = {.iov_base = reply, .iov_len = sizeof(*reply)};
>  	struct iov_iter to;
> -	int ret = 0;
> +	int result;
>  
> -	reply.magic = 0;
> -	iov_iter_kvec(&to, READ, &iov, 1, sizeof(reply));
> +	reply->magic = 0;
> +	iov_iter_kvec(&to, READ, &iov, 1, sizeof(*reply));
>  	result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL);
> -	if (result <= 0) {
> -		if (!nbd_disconnected(config))
> +	if (result < 0) {
> +		if (!nbd_disconnected(nbd->config))

The above is actually sort of functional change, I'd suggest to do it in one
single patch because sock_xmit() won't return zero.

-- 
Ming