From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f44.google.com (mail-wm1-f44.google.com [209.85.128.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AE4EE255E20; Tue, 11 Mar 2025 17:23:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741713841; cv=none; b=dRszGBJVRH1WroNxrZ9f592pair2wS2Mnmq31JEhNTqTmsOfHcyc4o+hfzbg7LUnubKfhf7AH5wgPNbvTIqyaUETaYdoRQalcCCVmYISdyVYvLbvX10g0TuSgjr911paoKsASyhIFxn7vs7PUKiwASROXk4y//7W7rwujKZUQ68= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741713841; c=relaxed/simple; bh=owns9l5JLbWYp17TZuEzyhli5LeKH4b9XdYYGM2SdTk=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=dEW0AJeadrPl01ZlWMJzsWGAte3rb8tRqgeuVjZnezgqegMohYuMhsnnL0WW6mzn4WPopioU9IjGJd4SzfEzf10R9gpcJvJHfRfsTkny53XUFbeaxI+mDriln2QUMoXA6GvUGDSj2ptf3hmrYDMbpR3dvOXNL+IxhYujafJRnEE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=d4XuMbUo; arc=none smtp.client-ip=209.85.128.44 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="d4XuMbUo" Received: by mail-wm1-f44.google.com with SMTP id 5b1f17b1804b1-4394036c0efso34857515e9.2; Tue, 11 Mar 2025 10:23:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1741713838; x=1742318638; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:content-language:references :cc:to:subject:from:user-agent:mime-version:date:message-id:from:to :cc:subject:date:message-id:reply-to; bh=2CblXRDFSbYzBfdZvOZoTbib8TKXWZ1Do7JX0N+BLKY=; b=d4XuMbUoBqUpKKWoFYNfWAbTXK3mS3KEReiFjkzbPB7gBOA+NQAf5CkS0d5+PsFF8P u2XP7BbyxeeUfc2S/vtt5QRsiaq6HR8e1/kFWBMwmmnHTWl15Fy7awI/RoFWE6sarNoj arf4vzzl7UHE7CKtG4d4lPvY0TsCJpeTvSHWuKae9YjnkRqwhS3VaOGqqhZJVGUWI2hU mUecpSANozejnJ+pD9UVXPSsfDo0zOKN4g88Tqt79Bkt02Ca2knfi6Auo1kHSsLdj7Qm MM4btfJ6rprNLTU9jdN72i6Kb2fVth85vJQJiSgQl5v51ByL7QOdU2ox9Fdzq1f7lm4W tFQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741713838; x=1742318638; h=content-transfer-encoding:in-reply-to:content-language:references :cc:to:subject:from:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=2CblXRDFSbYzBfdZvOZoTbib8TKXWZ1Do7JX0N+BLKY=; b=NeHhQgUf/Z6O6Hu5v6E6+HhgP5wYhP0SCfnp3YRIkgoQmCX0zt1QuNuNv/v4YoI7Vu oVUcBFR/gpMwz/qTF+CxmfzTHotirw9Pnw7QnF/dkEUzLLGoh5Su3UUbZKlm/1Km30+O UwqqG/Yc6hIem072VAI/pGAZT/9NwXRGVwDLQs48Xzz+h22++8sNfvLq44zd7E6a8zBx hbCYZ+H5D9T86qVzBxTmpWCykU74uhh8xIOAo3OjCNWpxX45p5pRdgdBkE118f15NsoJ s/EIGtUKgbYJxW2+XPoVLEhf80lMugXp+8G9WwpYPEFyTzt70UdRVnnwfOlQCsnGh//V 6dCw== X-Forwarded-Encrypted: i=1; AJvYcCXDAqCf+IgxDKugK5sSL2hJ/n8wdu97R8PCT1aaynDoKyEQGoeahmq5rkQmFKpmv91PVx0MfOw=@vger.kernel.org X-Gm-Message-State: AOJu0Yy+ZEEEHk4JDm/87+PV/AyG007P7ipuLBuXqs1GPH0XL+URG0bu uugIqa3ylPct+NycTB6nm+fc6EZ8q7ZRtyp6KHaRHFERqnQ428TS X-Gm-Gg: ASbGnctKDWxHGbAg4Blr3rFc+sqddHmHlc9XDoHpjTY1Zk+SeZQu6HBo6XsS5WNICe6 hYofHgzMiiP3UJDafQTxyFgY6LtN7cdLWa0Y+LtguOqQDT4YS4pxVe2k3b73H3I99hJYbFFIhvH 3gISeQ6WcSDOyOflwYBlIOFUce4URMcbez7zRUXse2/s8ytMEu3Z7t7ezb3pzOUT44F3CtWzOuM R6UBOhHKQHvWvF4F8TfnLp9KqttBct8SJf2kiWYbwRO37U7ENYgdhKddw8N+eIwlF/E90NH9Ppq 2DYJAYhoQBfwlrurCkjotb5ndxE/HNB8sd0NuIvpXMF+YS/NPMeks6pP36cmY62k9NpKhROTJm9 1y0Cem4bI1Mc= X-Google-Smtp-Source: AGHT+IHmQIwKqmpw/iCa+vydvbfQuzaYeiFEWI+fVAggDgqfNeIzbmu5lpU7cflubg+ifd7aRx+85w== X-Received: by 2002:a5d:5886:0:b0:391:4674:b136 with SMTP id ffacd0b85a97d-3914674b5f1mr8616572f8f.29.1741713837608; Tue, 11 Mar 2025 10:23:57 -0700 (PDT) Received: from [93.173.93.237] (93-173-93-237.bb.netvision.net.il. [93.173.93.237]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3912bfb79cfsm18745734f8f.10.2025.03.11.10.23.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Mar 2025 10:23:57 -0700 (PDT) Message-ID: Date: Tue, 11 Mar 2025 19:23:20 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 From: Eli Billauer Subject: Re: [PATCH v2] char: xillybus: Fix error handling in xillybus_init_chrdev() To: Ma Ke , arnd@arndb.de, gregkh@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, stable@vger.kernel.org References: <20250311013935.219615-1-make24@iscas.ac.cn> Content-Language: en-US In-Reply-To: <20250311013935.219615-1-make24@iscas.ac.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hello, In what way is this better? cdev_del() calls cdev_unmap() to undo the mapping that a successful call to cdev_add() performs, but that's unnecessary, because the whole point is that the latter failed. And then cdev_del() calls kobject_put(), and then returns. So the existing code calls kobject_put() directly, achieving the same effect. It's a matter of coding style. Which is better? I don't know. What is the common convention in the kernel? Not clear either. For example, in fs/fuse/cuse.c a failure of cdev_add() leads to a call to cdev_del(), like you suggested. However, in uio/uio.c the same scenario is handled by a call to kobject_put(), exactly as in my driver. Has this topic been discussed in the past? Any decision made? Besides, if we remove the call to kobject_put(), so should the comment explaining it. Regards, Eli On 11/03/2025 3:39, Ma Ke wrote: > After cdev_alloc() succeed and cdev_add() failed, call cdev_del() to > remove unit->cdev from the system properly. > > Found by code review. > > Cc: stable@vger.kernel.org > Fixes: 8cb5d216ab33 ("char: xillybus: Move class-related functions to new xillybus_class.c") > Signed-off-by: Ma Ke > --- > Changes in v2: > - modified the patch as suggestions to avoid UAF. > --- > drivers/char/xillybus/xillybus_class.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/char/xillybus/xillybus_class.c b/drivers/char/xillybus/xillybus_class.c > index c92a628e389e..356af6551b0d 100644 > --- a/drivers/char/xillybus/xillybus_class.c > +++ b/drivers/char/xillybus/xillybus_class.c > @@ -104,8 +104,7 @@ int xillybus_init_chrdev(struct device *dev, > if (rc) { > dev_err(dev, "Failed to add cdev.\n"); > /* kobject_put() is normally done by cdev_del() */ > - kobject_put(&unit->cdev->kobj); > - goto unregister_chrdev; > + goto err_cdev; > } > > for (i = 0; i < num_nodes; i++) { > @@ -157,6 +156,7 @@ int xillybus_init_chrdev(struct device *dev, > device_destroy(&xillybus_class, MKDEV(unit->major, > i + unit->lowest_minor)); > > +err_cdev: > cdev_del(unit->cdev); > > unregister_chrdev: