2014-12-30 12:34:51

by Peter Hurley

Subject: [PATCH] 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 <[email protected]>
Signed-off-by: Peter Hurley <[email protected]>
---
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

2014-12-30 15:15:20

by Peter Hurley

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

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

2014-12-30 15:39:42

by Peter Hurley

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 <[email protected]>
Signed-off-by: Peter Hurley <[email protected]>
---
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