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| author | Jann Horn <jannh@google.com> | 2020-12-03 02:25:04 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-12-04 17:38:48 +0100 |
| commit | 54ffccbf053b5b6ca4f6e45094b942fab92a25fc (patch) | |
| tree | b30e76730582ec6960a35741dea3023040afbaf0 | |
| parent | 418baf2c28f3473039f2f7377760bd8f6897ae18 (diff) | |
| download | linux-54ffccbf053b5b6ca4f6e45094b942fab92a25fc.tar.gz linux-54ffccbf053b5b6ca4f6e45094b942fab92a25fc.tar.bz2 linux-54ffccbf053b5b6ca4f6e45094b942fab92a25fc.zip | |
tty: Fix ->pgrp locking in tiocspgrp()
tiocspgrp() takes two tty_struct pointers: One to the tty that userspace
passed to ioctl() (`tty`) and one to the TTY being changed (`real_tty`).
These pointers are different when ioctl() is called with a master fd.
To properly lock real_tty->pgrp, we must take real_tty->ctrl_lock.
This bug makes it possible for racing ioctl(TIOCSPGRP, ...) calls on
both sides of a PTY pair to corrupt the refcount of `struct pid`,
leading to use-after-free errors.
Fixes: 47f86834bbd4 ("redo locking of tty->pgrp")
CC: stable@kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_jobctrl.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/tty_jobctrl.c b/drivers/tty/tty_jobctrl.c index 28a23a0fef21..baadeea4a289 100644 --- a/drivers/tty/tty_jobctrl.c +++ b/drivers/tty/tty_jobctrl.c @@ -494,10 +494,10 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t if (session_of_pgrp(pgrp) != task_session(current)) goto out_unlock; retval = 0; - spin_lock_irq(&tty->ctrl_lock); + spin_lock_irq(&real_tty->ctrl_lock); put_pid(real_tty->pgrp); real_tty->pgrp = get_pid(pgrp); - spin_unlock_irq(&tty->ctrl_lock); + spin_unlock_irq(&real_tty->ctrl_lock); out_unlock: rcu_read_unlock(); return retval; |