Re: usb cdc-acm TIOCSSERIAL may wrongly report EPERM

[Greg KH <greg@kroah.com>]

On Wed, Feb 19, 2020 at 12:21:55PM +0100, Anthony Mallet wrote:
> On Wednesday 19 Feb 2020, at 10:56, Oliver Neukum wrote:
> > thank you for the detailed report about an unusual bug. Could you
> > test the attached patch?
> 
> I did not actually run it yet, but at first sight it seems that it will
> mishandle the ASYNC_CLOSING_WAIT_NONE case.
> 
> I attach patch 0002 which should handle all cases. I also inverted the
> logic of the CAP_SYS_ADMIN test, so that the delays are changed only
> if the rounded values (in 1/100th of seconds) are actually changed.
> 
> While I was there, I checked what other drivers do (it seems that many
> have the same issue). Something I also noticed is that the units are
> also maybe mishandled: internally the values seem to be in 'jiffies',
> not in msecs. See for instance:
> https://github.com/torvalds/linux/blob/701a9c8092ddf299d7f90ab2d66b19b4526d1186/drivers/tty/serial/serial_core.c#L780
> 
> So I added patch 0001 that uses the jiffies conversion functions. If
> you prefer to discuss this in a separate thread please tell me, I will
> redo just patch 0002 without this change.
> 
> 
> > I have taken the liberty of presuming to add your 'Reported-and-tested-by'.
> 
> Yes, no problem. Thank you.
> I hope my patches follow the required format, I'm not sure about all
> the details.


Hi,

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