linux-kernel - Re: [PATCH] staging: pi433: add rw semaphore fixing concurrency issues

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Message-ID: <255415.1527859942@turing-police.cc.vt.edu>
Date:   Fri, 01 Jun 2018 09:32:22 -0400
From:   valdis.kletnieks@...edu
To:     Hugo Lefeuvre <hle@....eu.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kernelnewbies@...nelnewbies.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: pi433: add rw semaphore fixing concurrency issues

On Fri, 01 Jun 2018 08:50:37 -0400, Hugo Lefeuvre said:

> @@ -805,9 +809,11 @@ pi433_read(struct file *filp, char __user *buf, size_t size, loff_t *f_pos)
>  	if (bytes_received > 0) {
>  		retval = copy_to_user(buf, device->rx_buffer, bytes_received);
>  		if (retval)
> +			up_read(&instance->instance_sem);
>  			return -EFAULT;
>  	}
>
> +	up_read(&instance->instance_sem);
>  	return bytes_received;
>  }

This doesn't do what you think.

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