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 C795939185A; Wed, 3 Jun 2026 06:12:28 +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=1780467149; cv=none; b=CgzZk+NwcK0WYiTy0nwlFEOAEOI7oahDsa/wsR+Cq3jVUhQqE9YkndVmGqCglOIBGO8ZNjN+HA/2/4WhzV0jR1lkfmjxnasuJ863siwAIkfcn2ZZ+p1RH8NILX6lUFlZYJxZdmV171jqiO8Pj4dsMPi8ioe6UaJyt1VfS5XSEqM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780467149; c=relaxed/simple; bh=lWua7L1jv5UtNvdc6yeGGeYTxb77zzMx5sRkHDfVUgw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lC2OE+p1KwDy9TSn+rMz4Bxc8BvC1eGVVVrXlQfvL4hwCcAEvlu8jQCZyLFRQxNXen9pqtvuW2h4DvzPItcRY9NaakKoAvP8u5d/yniEv92V9Qj8arssW3tVHHtznrDnus4dzTsGUt49AvSHZ8TBXwCxd4L3Pe+dX6YP+MPcTNw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fnaPve3u; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fnaPve3u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E6911F00893; Wed, 3 Jun 2026 06:12:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780467148; bh=xblQ9U4dvtYKZ4bHc3qWJV+1Pl6Dr159OoqxR5Vhjfk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=fnaPve3ubog03IU7GfDdY5x164tyQON11uSlB5+rMmYMAJKs8ynvEM0nYwL/dykl9 JV2oGm60IqG0mUDIyxCCqYnK5cGZKXkCsrzbxoKJWl4KwDidRTXa7vxCpU/WewZsNt 00PuTtHPFqPNiAgA4bYXVosGn7U/fNMgP8zLVovDpGXUqD7mlBKRhRZAmXLIFx16Jj EeptElYp794Ni8OVMtFcBrLiMpTuhyu5Y8u6nFUxpqJsTQFKtwQS/C8VeKFF4EKALf 17vc1d4mn1ETDZgGiLau6HIPoBOpuFWwrVGCfIMG3Jr/F+mYYQ199Liq6SRvmqa028 nOsKbw8Lg3Z6g== Message-ID: Date: Wed, 3 Jun 2026 08:12:24 +0200 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] tty: vt: hold tty reference for keyboard callbacks To: Morduan Zang , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, syzkaller-bugs@googlegroups.com, syzbot+2932e8970a6398db95c3@syzkaller.appspotmail.com, Zhan Jun References: <5186FF3C10B2F8A0+20260602061539.1500845-1-zhangdandan@uniontech.com> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 02. 06. 26, 8:15, Morduan Zang wrote: > From: Zhan Jun > > syzbot reported a use-after-free in stop_tty() when the VT > keyboard path handles the hold key. > > The keyboard event path reads vc->port.tty under kbd_event_lock, > but con_shutdown() clears the pointer under console_lock and the tty > can be released after the final close. The keyboard lock therefore > does not protect the tty lifetime. > > Let the VT port own a tty reference by using tty_port_tty_set() when > installing and shutting down the console tty. Use tty_port_tty_get() > in the keyboard paths before dereferencing vc->port.tty and drop the > reference after the last use. > > Reported-by: syzbot+2932e8970a6398db95c3@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/6a1dde0d.bd48a97d.14881d.0005.GAE@google.com/ > Signed-off-by: Zhan Jun > --- > drivers/tty/vt/keyboard.c | 17 ++++++++++++----- > drivers/tty/vt/vt.c | 4 ++-- > 2 files changed, 14 insertions(+), 7 deletions(-) > > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c > index dfdea0842149..19f8df9706ee 100644 > --- a/drivers/tty/vt/keyboard.c > +++ b/drivers/tty/vt/keyboard.c > @@ -509,9 +509,13 @@ static void fn_show_ptregs(struct vc_data *vc) > > static void fn_hold(struct vc_data *vc) > { > - struct tty_struct *tty = vc->port.tty; > + struct tty_struct *tty; > + > + if (rep) > + return; > > - if (rep || !tty) > + tty = tty_port_tty_get(&vc->port); We have guards (tty_port_tty) and you should use those. thanks, -- js suse labs