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USB: cdc-acm: fix unprivileged TIOCCSERIAL 

[ Upstream commit dd5619582d60007139f0447382d2839f4f9e339b ]

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: ba2d8ce9db ("cdc-acm: implement TIOCSSERIAL to avoid blocking close(2)")
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210408131602.27956-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Johan Hovold 2021-04-08 15:16:01 +02:00 committed by Greg Kroah-Hartman
parent 9aa1552034
commit 8abef571fd
1 changed files with 0 additions and 2 deletions
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2
drivers/usb/class/cdc-acm.c
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@ -954,8 +954,6 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
if ((close_delay != acm->port.close_delay) ||
(closing_wait != acm->port.closing_wait))
retval = -EPERM;
else
retval = -EOPNOTSUPP;
} else {
acm->port.close_delay = close_delay;
acm->port.closing_wait = closing_wait;