linux-kernel - Re: [PATCH 3/3] tty_lock: Localise the lock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 7 May 2012 18:03:07 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH 3/3] tty_lock: Localise the lock

Hi Alan,

On Thu, May 3, 2012 at 11:24 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
> index 5505ffc..d6fa842 100644
> --- a/drivers/tty/pty.c
> +++ b/drivers/tty/pty.c
> @@ -62,9 +63,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
>                        mutex_unlock(&devpts_mutex);
>                }
>  #endif
> -               tty_unlock();
>                tty_vhangup(tty->link);
> -               tty_lock();
>        }
>  }

I don't believe that this change is correct.

Consider the following scenario:

tty_release -> tty_lock -> pty_close -> tty_vhangup -> tty_lock

Which would cause a deadlock.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/