linux-kernel - Re: [PATCH v2 2/3] USB: cdc-acm: fix unprivileged TIOCCSERIAL

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Date:   Thu, 08 Apr 2021 15:32:26 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] USB: cdc-acm: fix unprivileged TIOCCSERIAL

Am Donnerstag, den 08.04.2021, 15:16 +0200 schrieb Johan Hovold:
> TIOCSSERIAL is a horrid, underspecified, legacy interface which for most
> serial devices is only useful for setting the close_delay and
> closing_wait parameters.
> 
> A non-privileged user has only ever been able to set the since long
> deprecated ASYNC_SPD flags and trying to change any other *supported*
> feature should result in -EPERM being returned. Setting the current
> values for any supported features should return success.
> 
> Fix the cdc-acm implementation which instead indicated that the
> TIOCSSERIAL ioctl was not even implemented when a non-privileged user
> set the current values.
> 
> Fixes: ba2d8ce9db0a ("cdc-acm: implement TIOCSSERIAL to avoid blocking close(2)")
> Signed-off-by: Johan Hovold <johan@...nel.org>
Acked-by: Oliver Neukum <oneukum@...e.com>