From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C1AE1253340; Fri, 31 Jul 2026 08:28:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785486517; cv=none; b=qR/HthdbMq/TcM4Sibx+8zlafDaGfpZ9tHt5XMupOfnCBYbch2q66K9glWlt7zyVhwKP8kuAPQV48chnFALIi+9YNSKEubvX8ZTyMwl7E9nJEaY5jzVmgKv9Eho5c/29BUg2UH4vI6+NPM1bAsJKlItIXqCJHjH/c+w6NN7RGbE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785486517; c=relaxed/simple; bh=rHAWX+QSHMAFDUyI19EU53mZcTLdsFUVbBf3N4hX9Ng=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=O2YzalAn5bASHRmOZ6BmKqEXdVYQ+CHN+o77NwPWZ/V/R9JkMBo7ikSSwk6WFdOoKPe55fPluniKFwuKkpyt2afx12UQlrcNOmIcaZbuzNqbjQBTH6YHcEVseMb1wkWtPt4iGtYM1cepkeaRAhS8hCMe2xDXFHIbIj9bBz4zOOk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vvOlp29u; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vvOlp29u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFEC41F00A3A; Fri, 31 Jul 2026 08:28:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785486516; bh=8GDTRfAP7dRgN9+1b/AB2a68zvYVBgQcHw0U9xaHWwk=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=vvOlp29uHZIUZ1trLTC6hJxHXDNqxuAekYKQTGuxIw7lCmE5isQzTf2mFXFOhRmYc hlzkoEilTe2QDKE2t69ERfxpQ9DU/s6+xDaUdzTVNC33Thn4c8VnjncW0MmfPhhud1 XADXlD8/9pIsIXG53IQBuZ3yddLvQ/hpEo/4Oya4= Date: Fri, 31 Jul 2026 10:28:22 +0200 From: Greg Kroah-Hartman To: Jiri Slaby Cc: Markus Probst , linux-serial@vger.kernel.org, Rob Herring , linux-kernel@vger.kernel.org, Joshua Rogers , stable Subject: Re: [PATCH 2/2] serdev: use tty_port_tty_get() in ttyport_write_buf() to prevent UAF Message-ID: <2026073132-nucleus-retying-680c@gregkh> References: <20260731-aisle-tty-serdev-v1-0-2401a3189327@linuxfoundation.org> <20260731-aisle-tty-serdev-v1-2-2401a3189327@linuxfoundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jul 31, 2026 at 10:24:02AM +0200, Jiri Slaby wrote: > On 31. 07. 26, 10:06, Greg Kroah-Hartman wrote: > > From: Joshua Rogers > > > > ttyport_write_buf() snapshots serport->tty as a raw pointer without > > taking a reference, while ttyport_close() can concurrently release the > > tty via tty_release_struct(), leading to a use-after-free. Use > > tty_port_tty_get() to obtain a reference-counted tty pointer, matching > > the pattern already used by ttyport_write_wakeup(). > > > > Assisted-by: AISLE:Snapshot > > Cc: stable > > Signed-off-by: Joshua Rogers > > Signed-off-by: Greg Kroah-Hartman > > --- > > drivers/tty/serdev/serdev-ttyport.c | 12 ++++++++++-- > > 1 file changed, 10 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c > > index 48ce5b3f8308..4d37c8130dd7 100644 > > --- a/drivers/tty/serdev/serdev-ttyport.c > > +++ b/drivers/tty/serdev/serdev-ttyport.c > > @@ -85,13 +85,21 @@ static const struct tty_port_client_operations client_ops = { > > static ssize_t ttyport_write_buf(struct serdev_controller *ctrl, const u8 *data, size_t len) > > { > > struct serport *serport = serdev_controller_get_drvdata(ctrl); > > - struct tty_struct *tty = serport->tty; > > + struct tty_struct *tty; > > + ssize_t ret; > > if (!test_bit(SERPORT_ACTIVE, &serport->flags)) > > return 0; > > + tty = tty_port_tty_get(serport->port); > > + if (!tty) > > + return 0; > > + > > set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); > > - return tty->ops->write(serport->tty, data, len); > > + ret = tty->ops->write(tty, data, len); > > + tty_kref_put(tty); > > Here, > > scope_guard(tty_port_tty, serport->port) { > struct tty_struct *tty = scoped_tty(); > > set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); > return tty->ops->write(serport->tty, data, len); > } > > return 0; > > appears to be cleaner. Yes, much cleaner. LLMs really don't know about "modern" kernel coding styles (they always use min_t() and don't like guard() code). I'll respin this and do a new version in a few days, thanks. greg k-h