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Subject[PATCH 1/1] TTY: fix PTY hangup vs close race
Date
Commit d3bda5298 (TTY: get rid of BTM around devpts_*) moved
devpts_pty_kill out of BTM, but the BTM was not protecting only
devpts_pty_kill, but also tty->link. Hence move the function back at
this late stage until this gets resolved properly some time later.

I was confused by tty_vhangup(tty->link) outside BTM. But inside of
tty_vhangup, there is a check for tty == NULL. But we cannot add such
a check here. We have to have the tty and free the devpts node...

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Sasha Levin <levinsasha928@gmail.com>
---
drivers/tty/pty.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index fa1bd2e..95037aa 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -54,8 +54,9 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
wake_up_interruptible(&tty->link->write_wait);
if (tty->driver->subtype == PTY_TYPE_MASTER) {
set_bit(TTY_OTHER_CLOSED, &tty->flags);
- tty_unlock();
+ /* BTM protects tty->link here */
devpts_pty_kill(tty->link);
+ tty_unlock();
tty_vhangup(tty->link);
tty_lock();
}
--
1.7.9



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