From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from vps0.lunn.ch (vps0.lunn.ch [156.67.10.101]) (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 009E041C71; Wed, 26 Feb 2025 13:43:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=156.67.10.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740577421; cv=none; b=FYjjDYxn/fO5Lo+a0J1K3p0B48RvBj/ECYvfw5kBTc8BmT9Gy//GFO3E4EePS0cvXT9m0jDwhe6heFvdXfCxRBFAFM66NXEmNNJv/YNm3zCe6qkZ+TKmtIJrpNyMDKI13rC/VR5AEFsJ3j6Ei519cuO9LEzhKrfXIS3Btgt86ZU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740577421; c=relaxed/simple; bh=C1RgbLR6GSfvgGMUX8LxeDVo7GdVzjmW06YGox9WhSA=; h=Date:From:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Md+QrwwDR005Mwl2QpnxTVImF9KRaAQsRWAc9yETJXQu6GpLzN6DmT7/UgEK+yPAuQkWDFCFqV8VsKQjzsEBPbWaVYw9Eb5jwdKIx52+n3+4tN6xUrxax4Q70xiRbmfFocgTVH1XB9nXLkF4mhv9BzCN2tLUDpMqaPCawSwhmeg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lunn.ch; spf=pass smtp.mailfrom=lunn.ch; dkim=pass (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b=O+J6C6YS; arc=none smtp.client-ip=156.67.10.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lunn.ch Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lunn.ch Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="O+J6C6YS" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:From:Date:From:Sender:Reply-To:Subject:Date: Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=+RM9fCd/pH/t1kXOr5ohz3w+lMtjBfCOedTcP39zAaM=; b=O+J6C6YSUoR+qkSnbq3xnBv7kq TK4+SebVazszU6RcdBlkTq5CUyf3NmIhIhYO4MGohY316oVlXE0KLvs6ss0yQ3ky3nYPY3QhgpeF9 eE9Sc7oXJ+d8EeSJgvEf/0+iAexlZBH/QGnIn08RsEP67gXc1wGFh+n+8SXiFA7yLrgA=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1tnHhD-000Gqa-Mm; Wed, 26 Feb 2025 14:43:31 +0100 Date: Wed, 26 Feb 2025 14:43:31 +0100 From: Andrew Lunn Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] net: fix uninitialised access in mii_nway_restart() Message-ID: <418ddcf6-e7c9-4a8e-ba1a-38a83cb2b5f8@lunn.ch> References: 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 Tue, Feb 18, 2025 at 12:19:57PM +0000, Qasim Ijaz wrote: > On Tue, Feb 18, 2025 at 02:10:08AM +0100, Andrew Lunn wrote: > > On Tue, Feb 18, 2025 at 12:24:43AM +0000, Qasim Ijaz wrote: > > > In mii_nway_restart() during the line: > > > > > > bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR); > > > > > > The code attempts to call mii->mdio_read which is ch9200_mdio_read(). > > > > > > ch9200_mdio_read() utilises a local buffer, which is initialised > > > with control_read(): > > > > > > unsigned char buff[2]; > > > > > > However buff is conditionally initialised inside control_read(): > > > > > > if (err == size) { > > > memcpy(data, buf, size); > > > } > > > > > > If the condition of "err == size" is not met, then buff remains > > > uninitialised. Once this happens the uninitialised buff is accessed > > > and returned during ch9200_mdio_read(): > > > > > > return (buff[0] | buff[1] << 8); > > > > > > The problem stems from the fact that ch9200_mdio_read() ignores the > > > return value of control_read(), leading to uinit-access of buff. > > > > > > To fix this we should check the return value of control_read() > > > and return early on error. > > > > What about get_mac_address()? > > > > If you find a bug, it is a good idea to look around and see if there > > are any more instances of the same bug. I could be wrong, but it seems > > like get_mac_address() suffers from the same problem? > > Thank you for the feedback Andrew. I checked get_mac_address() before > sending this patch and to me it looks like it does check the return value of > control_read(). It accumulates the return value of each control_read() call into > rd_mac_len and then checks if it not equal to what is expected (ETH_ALEN which is 6), > I believe each call should return 2. It is unlikely a real device could trigger an issue, but a USB Rubber Ducky might be able to. So the question is, are you interested in protecting against malicious devices, or just making a static analyser happy? Feel free to submit the patch as is. Andrew