linux-kernel - Re: [BUG] copy_file_range with sysfs file as input

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Message-ID: <YBpnBUD+QoMW9NtL@kroah.com>
Date:   Wed, 3 Feb 2021 10:04:05 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Nicolas Boichat <drinkcat@...omium.org>
Cc:     "Darrick J. Wong" <djwong@...nel.org>,
        linux-fsdevel@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        Amir Goldstein <amir73il@...il.com>,
        Dave Chinner <dchinner@...hat.com>,
        Luis Lozano <llozano@...omium.org>, iant@...gle.com
Subject: Re: [BUG] copy_file_range with sysfs file as input

On Mon, Jan 25, 2021 at 03:54:31PM +0800, Nicolas Boichat wrote:
> Hi copy_file_range experts,
> 
> We hit this interesting issue when upgrading Go compiler from 1.13 to
> 1.15 [1]. Basically we use Go's `io.Copy` to copy the content of
> `/sys/kernel/debug/tracing/trace` to a temporary file.

Nit, the above file is NOT a sysfs file.  Odds are it is either a
debugfs, or a tracefs file, please check your mounts to determine which
it is, as that matters a lot on the kernel backend side for trying to
figure out what is going on here :)

thanks,

greg k-h