From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D221DC072A4 for ; Wed, 22 May 2019 08:16:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ADA5320815 for ; Wed, 22 May 2019 08:16:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728727AbfEVIQC (ORCPT ); Wed, 22 May 2019 04:16:02 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:40120 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726552AbfEVIQB (ORCPT ); Wed, 22 May 2019 04:16:01 -0400 Received: by mail-wr1-f68.google.com with SMTP id f10so1172115wre.7 for ; Wed, 22 May 2019 01:15:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=L61GZ1vGWhSEJqecA5eKfOLhoaeorDC4hNTYi6dhVcY=; b=D+cJmbHuzT4uWZspwIy31YKH8F721lbOAduk/G1UaXA0SNkH2RcPpl/oVUGOWJ3xx2 bHEuSf4dbOzJt5juTp/nHnObm9LMm7KdNYH1XPjKOhDzyJwU0TSMzRTTO/U3BGwaW6YQ 9Zh8Ndc+iejWe9wVGegFFdCWogMP8vujO7wZ/ITjqzRwRpCUm4VR5YSvKHK3EPZONt4l eJSOZcYh6KZwvMSUdNkKygSj0G7DoYt437izcVyLpnjZNd1zvngPFBy9BgX5VKes3Z+R vN3OdaKnrGoP4TEX1dBPpRdgwk8UfLsgwS5Aj8p9xcjr4MvYx0Ugx2dHPh3hysl9kAT0 X3+w== X-Gm-Message-State: APjAAAVQ9EIhTaWU5SU1vUKOu3iXKQFz7E4GEXTs2U0hgnJ5a2/XkbYd di/nqc7ZuY1cHyRB+1YBZ7mXj5SG X-Google-Smtp-Source: APXvYqzP5eAxt+QUdNKDPImk4DLyQ9IrS3d/xiCvj7cG/GwGarLagqzX4gxsF0Qj0WVblbYGVE5LMw== X-Received: by 2002:a5d:54c9:: with SMTP id x9mr35515424wrv.266.1558512959021; Wed, 22 May 2019 01:15:59 -0700 (PDT) Received: from ?IPv6:2a0b:e7c0:0:107::49? ([2a0b:e7c0:0:107::49]) by smtp.gmail.com with ESMTPSA id a22sm4984007wma.41.2019.05.22.01.15.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 May 2019 01:15:57 -0700 (PDT) Subject: Re: [PATCH] tty_io: Fix a missing-check bug in drivers/tty/tty_io.c To: Gen Zhang Cc: linux-kernel@vger.kernel.org References: <20190522014006.GB4093@zhanggen-UX430UQ> <20190522080656.GA5109@zhanggen-UX430UQ> From: Jiri Slaby Openpgp: preference=signencrypt Autocrypt: addr=jslaby@suse.cz; prefer-encrypt=mutual; keydata= mQINBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABtBtKaXJpIFNsYWJ5 IDxqc2xhYnlAc3VzZS5jej6JAjgEEwECACIFAk6S6NgCGwMGCwkIBwMCBhUIAgkKCwQWAgMB Ah4BAheAAAoJEL0lsQQGtHBJgDsP/j9wh0vzWXsOPO3rDpHjeC3BT5DKwjVN/KtP7uZttlkB duReCYMTZGzSrmK27QhCflZ7Tw0Naq4FtmQSH8dkqVFugirhlCOGSnDYiZAAubjTrNLTqf7e 5poQxE8mmniH/Asg4KufD9bpxSIi7gYIzaY3hqvYbVF1vYwaMTujojlixvesf0AFlE4x8WKs wpk43fmo0ZLcwObTnC3Hl1JBsPujCVY8t4E7zmLm7kOB+8EHaHiRZ4fFDWweuTzRDIJtVmrH LWvRDAYg+IH3SoxtdJe28xD9KoJw4jOX1URuzIU6dklQAnsKVqxz/rpp1+UVV6Ky6OBEFuoR 613qxHCFuPbkRdpKmHyE0UzmniJgMif3v0zm/+1A/VIxpyN74cgwxjhxhj/XZWN/LnFuER1W zTHcwaQNjq/I62AiPec5KgxtDeV+VllpKmFOtJ194nm9QM9oDSRBMzrG/2AY/6GgOdZ0+qe+ 4BpXyt8TmqkWHIsVpE7I5zVDgKE/YTyhDuqYUaWMoI19bUlBBUQfdgdgSKRMJX4vE72dl8BZ +/ONKWECTQ0hYntShkmdczcUEsWjtIwZvFOqgGDbev46skyakWyod6vSbOJtEHmEq04NegUD al3W7Y/FKSO8NqcfrsRNFWHZ3bZ2Q5X0tR6fc6gnZkNEtOm5fcWLY+NVz4HLaKrJuQINBE6S 54YBEADPnA1iy/lr3PXC4QNjl2f4DJruzW2Co37YdVMjrgXeXpiDvneEXxTNNlxUyLeDMcIQ K8obCkEHAOIkDZXZG8nr4mKzyloy040V0+XA9paVs6/ice5l+yJ1eSTs9UKvj/pyVmCAY1Co SNN7sfPaefAmIpduGacp9heXF+1Pop2PJSSAcCzwZ3PWdAJ/w1Z1Dg/tMCHGFZ2QCg4iFzg5 Bqk4N34WcG24vigIbRzxTNnxsNlU1H+tiB81fngUp2pszzgXNV7CWCkaNxRzXi7kvH+MFHu2 1m/TuujzxSv0ZHqjV+mpJBQX/VX62da0xCgMidrqn9RCNaJWJxDZOPtNCAWvgWrxkPFFvXRl t52z637jleVFL257EkMI+u6UnawUKopa+Tf+R/c+1Qg0NHYbiTbbw0pU39olBQaoJN7JpZ99 T1GIlT6zD9FeI2tIvarTv0wdNa0308l00bas+d6juXRrGIpYiTuWlJofLMFaaLYCuP+e4d8x rGlzvTxoJ5wHanilSE2hUy2NSEoPj7W+CqJYojo6wTJkFEiVbZFFzKwjAnrjwxh6O9/V3O+Z XB5RrjN8hAf/4bSo8qa2y3i39cuMT8k3nhec4P9M7UWTSmYnIBJsclDQRx5wSh0Mc9Y/psx9 B42WbV4xrtiiydfBtO6tH6c9mT5Ng+d1sN/VTSPyfQARAQABiQIfBBgBAgAJBQJOkueGAhsM AAoJEL0lsQQGtHBJN7UQAIDvgxaW8iGuEZZ36XFtewH56WYvVUefs6+Pep9ox/9ZXcETv0vk DUgPKnQAajG/ViOATWqADYHINAEuNvTKtLWmlipAI5JBgE+5g9UOT4i69OmP/is3a/dHlFZ3 qjNk1EEGyvioeycJhla0RjakKw5PoETbypxsBTXk5EyrSdD/I2Hez9YGW/RcI/WC8Y4Z/7FS ITZhASwaCOzy/vX2yC6iTx4AMFt+a6Z6uH/xGE8pG5NbGtd02r+m7SfuEDoG3Hs1iMGecPyV XxCVvSV6dwRQFc0UOZ1a6ywwCWfGOYqFnJvfSbUiCMV8bfRSWhnNQYLIuSv/nckyi8CzCYIg c21cfBvnwiSfWLZTTj1oWyj5a0PPgGOdgGoIvVjYXul3yXYeYOqbYjiC5t99JpEeIFupxIGV ciMk6t3pDrq7n7Vi/faqT+c4vnjazJi0UMfYnnAzYBa9+NkfW0w5W9Uy7kW/v7SffH/2yFiK 9HKkJqkN9xYEYaxtfl5pelF8idoxMZpTvCZY7jhnl2IemZCBMs6s338wS12Qro5WEAxV6cjD VSdmcD5l9plhKGLmgVNCTe8DPv81oDn9s0cIRLg9wNnDtj8aIiH8lBHwfUkpn32iv0uMV6Ae sLxhDWfOR4N+wu1gzXWgLel4drkCJcuYK5IL1qaZDcuGR8RPo3jbFO7Y Message-ID: <3a3db304-9725-6a90-65ac-dff09ef31aae@suse.cz> Date: Wed, 22 May 2019 10:15:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190522080656.GA5109@zhanggen-UX430UQ> Content-Type: text/plain; charset=iso-8859-2 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22. 05. 19, 10:06, Gen Zhang wrote: > On Wed, May 22, 2019 at 06:25:36AM +0200, Jiri Slaby wrote: >> On 22. 05. 19, 3:40, Gen Zhang wrote: >>> In alloc_tty_struct(), tty->dev is assigned by tty_get_device(). And it >>> calls class_find_device(). And class_find_device() may return NULL. >>> And tty->dev is dereferenced in the following codes. When >>> tty_get_device() returns NULL, dereferencing this tty->dev null pointer >>> may cause the kernel go wrong. Thus we should check tty->dev. >>> Further, if tty_get_device() returns NULL, we should free tty and >>> return NULL. >>> >>> Signed-off-by: Gen Zhang >>> >>> --- >>> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c >>> index 033ac7e..1444b59 100644 >>> --- a/drivers/tty/tty_io.c >>> +++ b/drivers/tty/tty_io.c >>> @@ -3008,6 +3008,10 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx) >>> tty->index = idx; >>> tty_line_name(driver, idx, tty->name); >>> tty->dev = tty_get_device(tty); >>> + if (!tty->dev) { >>> + kfree(tty); >>> + return NULL; >>> + } >> >> This is incorrect, you introduced an ldisc reference leak. > Thanks for your reply, Jiri! > And what do you mean by an ldisc reference leak? I did't get the reason > of introducing it. Look at the top of alloc_tty_struct: there is tty_ldisc_init. If tty_get_device fails here, you have to call tty_ldisc_deinit. Better, you should add a failure-handling tail to this function and "goto" there. >> And can this happen at all? > I think tty_get_device() may happen to return NULL. Because it calls > class_find_device() and there's a chance class_find_device() returns > NULL. Sure, but can class_find_device return NULL in this tty case here? thanks, -- js suse labs