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


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