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SubjectRe: [PATCH v9 1/1] Add support for IPMB driver

> +static int receive_ipmb_request(struct ipmb_dev *ipmb_dev,
> + bool non_blocking,
> + struct ipmb_msg *ipmb_request)
> +{
> + struct ipmb_request_elem *queue_elem;
> + unsigned long flags;
> + int res;
> +
> + spin_lock_irqsave(&ipmb_dev->lock, flags);
> +
> + while (!atomic_read(&ipmb_dev->request_queue_len)) {

Am I overlooking something? Why are you protecting an atomic_read with a
spinlock?

> + spin_unlock_irqrestore(&ipmb_dev->lock, flags);
> +
> + if (non_blocking)
> + return -EAGAIN;
> +
> + res = wait_event_interruptible(ipmb_dev->wait_queue,
> + atomic_read(&ipmb_dev->request_queue_len));
> + if (res)
> + return res;
> +
> + spin_lock_irqsave(&ipmb_dev->lock, flags);
> + }

...

> + rq_sa = msg[RQ_SA_8BIT_IDX] >> 1;
> + netf_rq_lun = msg[NETFN_LUN_IDX];
> + /*
> + * subtract rq_sa and netf_rq_lun from the length of the msg passed to
> + * i2c_smbus_write_block_data_local
> + */
> + msg_len = msg[IPMB_MSG_LEN_IDX] - SMBUS_MSG_HEADER_LENGTH;
> +
> + strcpy(rq_client.name, "ipmb_requester");
> + rq_client.adapter = ipmb_dev->client->adapter;
> + rq_client.flags = ipmb_dev->client->flags;
> + rq_client.addr = rq_sa;

Is it possible to determine in a race-free way if rq_sa (which came from
userspace AFAIU) is really the address from which the request came in
(again if I understood all this correctly)?

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