[PATCH] tty: Prevent hw state corruption in exclusive mode reopen

[PATCH] tty: Prevent hw state corruption in exclusive mode reopen

[Peter Hurley]

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 | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 4f35b43..8629087 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2091,6 +2091,11 @@ retry_open:
 		goto err_file;
 	}
 
+	if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN)) {
+		retval = -EBUSY;
+		goto err_file;
+	}
+
 	tty_add_file(tty, filp);
 
 	check_tty_count(tty, __func__);
@@ -2106,10 +2111,6 @@ 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

Re: [PATCH] tty: Prevent hw state corruption in exclusive mode reopen

[Peter Hurley]

On 12/30/2014 07:34 AM, Peter Hurley wrote:
> 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.

Greg,

Please disregard. I'll redo a v2 that isn't broken.

Regards,
Peter Hurley

[PATCH v2] tty: Prevent hw state corruption in exclusive mode reopen

[Peter Hurley]

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

Re: [PATCH v2] tty: Prevent hw state corruption in exclusive mode reopen

[Shreyas Bethur]

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>