From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lj1-f180.google.com (mail-lj1-f180.google.com [209.85.208.180]) (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 B4D3172 for ; Sun, 22 Aug 2021 10:09:34 +0000 (UTC) Received: by mail-lj1-f180.google.com with SMTP id q21so25583738ljj.6 for ; Sun, 22 Aug 2021 03:09:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=vcNozNLiELsOkaLftabobubDY4L64Yc6cQ2FcWqWBwc=; b=AFzTJUh5WbeVl60l5ScI4OD/h0pdCopHPcUgEUZFjjGFgIUG/Am9kwC2//d8jRsMb/ GVLUwObKjQdbGvKU5v8p3ppN93tPqUg5WnEjut7KYGes8TlQXaM9pt5bzOQc0wnPbpwo +b/EopIXzIfVaKKOyj1uXR/2Khby+vAOi/opmcmKS43ZF3HOGtpgcv3lBLimPVIHs+nf WQXJwN+XFfMSoM+gfyo1RnFom70IC9xk45tWGwxJL7aO/s6g81QEGBQjMYGFCmeYSMVu IPwvvu55HKOO7asNeVUUU2gCr3y6Uafq2TqczBMWjNCPYwZ2lPj4993N8S+nxeSAoHjc W8xQ== 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:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=vcNozNLiELsOkaLftabobubDY4L64Yc6cQ2FcWqWBwc=; b=tPxiVgWJQOya1lhOPlzgmynpVFaKVFCF3FWosnrWTGFQYWCdh+OH2uWDfavvNguWfN VUZTWZAmL0QqVItq2icQ8tRJeTE8RA3wE+J2PAOJ2ELe/Y+a2xPozZKpEP8xmxHFp0gn 9evwuHSj9njhAh3Xvsy7a2+x48M2kIOKy7FYzBljjxS8DltoM2By4ZPxAlhtRTXpjZjT YO0N/JjMpv/3HJe6OB3RFnLT4ZCKOojtNW5OvhBOP5UldC4o3dSUU6f6e9zdC7ckHpwt KcJ5K1Ev4vJX7Jk39RkL4DEDCujzXd8RxtGIuyqQwKHDcmrDrFHWxhvYxAR7O5RKKITq rXeA== X-Gm-Message-State: AOAM531DK+m5km04i3iB29ayqZAvp/XCjiPAc67Ru1A7Tdi8sAXWGK2J WmUADH9rc2p5jO0Ke7hKouM= X-Google-Smtp-Source: ABdhPJxptblskllBGDsN7QLRA5pwdqKM080g9LWwy7oYDzbKhQBq+unHX2UY758PcBm36jHbvncoZg== X-Received: by 2002:a2e:a288:: with SMTP id k8mr22538870lja.315.1629626972669; Sun, 22 Aug 2021 03:09:32 -0700 (PDT) Received: from localhost.localdomain ([185.215.60.67]) by smtp.gmail.com with ESMTPSA id o6sm1268933lfo.110.2021.08.22.03.09.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Aug 2021 03:09:32 -0700 (PDT) Subject: Re: [PATCH RFC 0/3] staging: r8188eu: avoid uninit value bugs To: "Fabio M. De Francesco" , Larry.Finger@lwfinger.net, phil@philpotter.co.uk, gregkh@linuxfoundation.org, straube.linux@gmail.com Cc: linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, Martin Kaiser References: <10584649.zhyk0TxWeL@localhost.localdomain> From: Pavel Skripkin Message-ID: Date: Sun, 22 Aug 2021 13:09:29 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <10584649.zhyk0TxWeL@localhost.localdomain> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit On 8/22/21 12:53 PM, Fabio M. De Francesco wrote: > On Friday, August 20, 2021 7:07:28 PM CEST Pavel Skripkin wrote: >> Hi, Greg, Larry and Phillip! >> >> I noticed, that new staging driver was added like 3 weeks ago and I decided >> to look at the code, because drivers in staging directory are always buggy. >> >> The first thing I noticed is *no one* was checking read operations result, > but >> it can fail and driver may start writing random stack values into registers. > It >> can cause driver misbehavior or device misbehavior. > > After the messages I wrote yesterday, I had some minutes to look deeper at the > code that would be changed by these patches. > > I think that it does not look like that the driver could return "random stack > values into registers" and I think this entire series in unnecessary. > > As far as I understand this driver (though I must admit that I really don't > know how to write drivers, and I'm not interested in understanding - at the > moment, at least), all the usb_read*() call usbctrl_vendorreq() and the latter > *does* proper error checking before returning to the callers the read data. > > Please, look at the code copied from usbctrl_vendorreq() and pasted here (some > comments are mine): > > /* start of code */ > static int usbctrl_vendorreq(struct intf_hdl *pintfhdl, u16 value, void > *pdata, u16 len, u8 requesttype) > { > > /* test if everything is OK for transfers and setup the necessary variables */ > [...] > > status = usb_control_msg(udev, pipe, REALTEK_USB_VENQT_CMD_REQ, > reqtype, value, > REALTEK_USB_VENQT_CMD_IDX, > pIo_buf, len, > RTW_USB_CONTROL_MSG_TIMEOUT); > > if (status == len) { /* Success this control transfer. */ > rtw_reset_continual_urb_error(dvobjpriv); > if (requesttype == 0x01) > memcpy(pdata, pIo_buf, len); /* pdata > receives the read data */ > } else { /* error cases */ > > [...] > > } > /* end of code */ > > So, *I cannot ack this RFC*, unless maintainers say I'm missing something. > > Larry, Philip, since you have much more knowledge than me about r8188eu (and, > more in general, on device drivers) may you please say what you think about my > arguments against this series? > Hi, Fabio! Thank you for looking into this, but I still can see the case when pdata won't be initialized: pdata is initialized only in case of successful transfer, i.e len > 0. It means some data was received (maybe not full length, but anyway). In case of usb_control_msg() error (for example -ENOMEM) code only does this code block: if (status < 0) { if (status == (-ESHUTDOWN) || status == -ENODEV) { adapt->bSurpriseRemoved = true; } else { struct hal_data_8188e *haldata = GET_HAL_DATA(adapt); haldata->srestpriv.Wifi_Error_Status = USB_VEN_REQ_CMD_FAIL; } } And then just loops further. In case of 10 ENOMEM in a row,. passed pdata won't be initialized at all and driver doesn't do anything about it. I believe, it's not good approach to play with random values. We should somehow handle transfer errors all across the driver. If I am missing something, please, let me know :) With regards, Pavel Skripkin