linux-kernel - Re: [PATCH] tty: add lockdep annotations

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]

Message-ID: <20120601215620.305155c0@pyramind.ukuu.org.uk>
Date:	Fri, 1 Jun 2012 21:56:20 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jens Axboe <jaxboe@...ionio.com>
Subject: Re: [PATCH] tty: add lockdep annotations

> Yes, tty->driver deref is ok (tty points to valid memory), but crash is
> on tty->driver->ops (driver points to freed/illegal memory)
> 
> using slub_debug=FZPU, I can indeed see RDI=6b6b6b6b6b6b6b6b

driver and driver->ops is basically const and it's not what you'd expect
from a tty refcount bug. The driver side puts shouldn't have changed but
I'll take a look over that patch and the error paths closely again just
in case.

It could be that tty->driver is pointing at a valid but bogus location
but again its not something I'd expect.

> By the way, release_one_tty() uses the following racy code :
> 
> tty_driver_kref_put(driver);
> module_put(driver->owner);
> 
> I would use following patch to make sure bad things cant happen...

Agreed. Although we wouldn't be unloading console or pty so it's alas not
the real cause.


Alan
--
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/