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SubjectRe: [PATCH v2] tty: Prevent hw state corruption in exclusive mode reopen
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Peter Hurley <peter@hurleysoftware.com> wrote on 12/30/2014 09:39:25 AM:

> From: Peter Hurley <peter@hurleysoftware.com>
> To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
> Cc: Jiri Slaby <jslaby@suse.cz>, linux-kernel@vger.kernel.org,
> linux-serial@vger.kernel.org, Shreyas Bethur
> <shreyas.bethur@ni.com>, Peter Hurley <peter@hurleysoftware.com>
> Date: 12/30/2014 09:39 AM
> Subject: [PATCH v2] tty: Prevent hw state corruption in exclusive mode
reopen
>
> Exclusive mode ttys (TTY_EXCLUSIVE) do not allow further reopens;
> fail the condition before associating the file pointer and calling
> the driver open() method.
>
> Prevents DTR programming when the tty is already in exclusive mode.
>
> Reported-by: Shreyas Bethur <shreyas.bethur@ni.com>
> Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
> ---
> drivers/tty/tty_io.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 4f35b43..51f066a 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -1464,6 +1464,9 @@ static int tty_reopen(struct tty_struct *tty)
> driver->subtype == PTY_TYPE_MASTER)
> return -EIO;
>
> + if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
> + return -EBUSY;
> +
> tty->count++;
>
> WARN_ON(!tty->ldisc);
> @@ -2106,10 +2109,6 @@ retry_open:
> retval = -ENODEV;
> filp->f_flags = saved_flags;
>
> - if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) &&
> - !capable(CAP_SYS_ADMIN))
> - retval = -EBUSY;
> -
> if (retval) {
> #ifdef TTY_DEBUG_HANGUP
> printk(KERN_DEBUG "%s: error %d in opening %s...\n", __func__,
> --
> 2.2.1
>

Acked-by: Shreyas Bethur <shreyas.bethur@ni.com>



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