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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 78808C4338F for ; Tue, 24 Aug 2021 22:08:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4BB23611C8 for ; Tue, 24 Aug 2021 22:08:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238479AbhHXWI6 (ORCPT ); Tue, 24 Aug 2021 18:08:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235507AbhHXWIz (ORCPT ); Tue, 24 Aug 2021 18:08:55 -0400 Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2B3EFC061757 for ; Tue, 24 Aug 2021 15:08:11 -0700 (PDT) Received: by mail-pl1-x62f.google.com with SMTP id a5so13115819plh.5 for ; Tue, 24 Aug 2021 15:08:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=philpotter-co-uk.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=kYgNlhYCjdmXO4IIXLzxiUks/mikPCsz+I8vx+exU7k=; b=miJEWiUCmYLfwBr4/NJ6Q1mhlJGDwlrW4NA/zfvrPthvOsUMQJpumaGYAkKVryHAv3 Xsui/JHE8LDmcUBP3Ky0OZR/excgcdtkGXntcClRwJliv2V+x4tEG1QfR81HeByXQy6Q iRtIGpUwAwx2eAejEkxg6K0UFAUWk7ybS7P+ap5kjl5Pe2VGJz0hmWQeBAFOZXIglYBM vDxQeyRV/fvQUYihQSLYSCaGGDiSpWC+xP6OUYGYBqowlwAhdwgg3Ux0aFRIfgNjmgtB bYAXsiWcnKy65eFaViV3VUNbHsfiPHu26O+flkd7WLn1vekqGgJ8aEFxft1bH712v2UT iXIQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=kYgNlhYCjdmXO4IIXLzxiUks/mikPCsz+I8vx+exU7k=; b=MPnJuLUxTxyEO89jCI6EGoTWd8DN8VNlnv7yiVukT+D9Mz7ceLreSg9blLh5KshegC 7aXiOm4Hcrfw/W3JIzfXvbl1yv8NhxNeBv6dDeczF4BJOsQj77bR5CYIlWQ8dlu24H0Q /PTRtHklk/UOFGMb3Xarz1okEsHcPgamtwcoR+H9YyTqkLTsa5pE+ksFp4XPwOS3oExP Vf3ECwuGX2kFV6IcXKpiRsIVrS5VFI4mx6PzL9CZUI3NMWTE84tM2JK+Jhp+1xg66vRC PhD+FEBCLjEHgfoBWdxFHWoeDesWOz2iLcF/IhRGqAFlcbr/jSPHv8vamb/6FcpUbkNJ ysQA== X-Gm-Message-State: AOAM530onK3f3UtJEsbUQ/yQXeqSJKnNgPSQOfCl/xu1OhCHFU7voKUa 5eLW3+hmQ17ixizeOzk8kGJ7mtt9ZZHH/nd/NirBHg== X-Google-Smtp-Source: ABdhPJx39aSQgrstRV9TO2YQhI96WwKnQj2hL6WTESRHWFG68fPwMHL8QNV2sbihkycfOiLyqq8MmDlrYX/J24y2SYc= X-Received: by 2002:a17:90a:1b2e:: with SMTP id q43mr6764073pjq.217.1629842890628; Tue, 24 Aug 2021 15:08:10 -0700 (PDT) MIME-Version: 1.0 References: <2424268.2DCLMNk6Lg@localhost.localdomain> <2355365e-d75e-8d1b-aad8-6979b70f33ec@gmail.com> <3419359.n4KOUNuIW1@localhost.localdomain> <77da7c63-a5b1-a09d-39ec-32c5485b8eac@gmail.com> In-Reply-To: <77da7c63-a5b1-a09d-39ec-32c5485b8eac@gmail.com> From: Phillip Potter Date: Tue, 24 Aug 2021 23:07:59 +0100 Message-ID: Subject: Re: [PATCH RFC v2 5/6] staging: r8188eu: add error handling of rtw_read32 To: Pavel Skripkin Cc: "Fabio M. De Francesco" , Larry Finger , Greg KH , Michael Straube , "open list:STAGING SUBSYSTEM" , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 24 Aug 2021 at 09:47, Pavel Skripkin wrote: > > On 8/24/21 11:38 AM, Fabio M. De Francesco wrote: > > On Tuesday, August 24, 2021 8:40:18 AM CEST Pavel Skripkin wrote: > >> On 8/24/21 3:10 AM, Fabio M. De Francesco wrote: > >> > On Tuesday, August 24, 2021 1:33:46 AM CEST Phillip Potter wrote: > >> >> On Sun, 22 Aug 2021 at 15:36, Pavel Skripkin wrote: > >> >> > -static u32 usb_read32(struct intf_hdl *pintfhdl, u32 addr) > >> >> > +static int usb_read32(struct intf_hdl *pintfhdl, u32 addr, u32 *data) > >> >> > { > >> >> > u8 requesttype; > >> >> > u16 wvalue; > >> >> > u16 len; > >> >> > - __le32 data; > >> >> > + int res; > >> >> > + __le32 tmp; > >> >> > + > >> >> > + if (WARN_ON(unlikely(!data))) > >> >> > + return -EINVAL; > >> >> > > >> >> > requesttype = 0x01;/* read_in */ > >> >> > > >> >> > wvalue = (u16)(addr & 0x0000ffff); > >> >> > len = 4; > >> >> > > >> >> > - usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype); > >> >> > + res = usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype); > >> >> > + if (res < 0) { > >> >> > + dev_err(dvobj_to_dev(pintfhdl->pintf_dev), "Failed to read 32 bytes: %d\n", res); > >> >> > + } else { > >> >> > + /* Noone cares about positive return value */ > >> >> > + *data = le32_to_cpu(tmp); > >> >> > + res = 0; > >> >> > + } > >> >> > > >> >> > - return le32_to_cpu(data); > >> >> > + return res; > >> >> > } > >> >> > >> >> Dear Pavel, > >> >> > >> >> OK, found the issue with decoded stack trace after reviewing this > >> >> usb_read32 function. Your line: > >> >> res = usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype); > >> >> > >> >> should read: > >> >> res = usbctrl_vendorreq(pintfhdl, wvalue, &tmp, len, requesttype); > >> > > >> > Dear Philip, > >> > > >> > No, it should read: > >> > > >> > res = usbctrl_vendorreq(pintfhdl, wvalue, data, len, requesttype); > >> > > >> > I suspect that Pavel didn't notice he was reusing a line of the old code > >> > wth no due changes. > >> > > >> >> With this change, the driver runs fine with no crashes/oopses. I will > >> >> explain the issue but you can probably see already, so I hope I'm not > >> >> coming across as patronising, just trying to be helpful :-) > >> >> > >> >> Essentially, you are taking the address of the data function parameter > >> >> on this line with &data, a pointer to u32, which is giving you a > >> >> pointer to a pointer to u32 (u32 **) for this function parameter > >> >> variable. When passed to usbctrl_vendorreq, it is being passed to > >> >> memcpy inside this function as a void *, meaning that memcpy > >> >> subsequently overwrites the value of the memory address inside data to > >> >> point to a different location, which is problem when it is later > >> >> deferenced at: > >> >> *data = le32_to_cpu(tmp); > >> >> causing the OOPS > >> >> > >> >> Also, as written, you can probably see that tmp is uninitialised. This > >> >> looks like a typo, so guessing this wasn't your intention. Anyhow, > >> >> with that small change, usbctrl_vendorreq reads into tmp, which is > >> >> then passed to le32_to_cpu whose return value is stored via the > >> >> deferenced data ptr (which now has its original address within and not > >> >> inadvertently modified). Hope this helps, and I'd be happy to Ack the > >> >> series if you want to resend this patch. Many thanks. > >> > > >> > I think that another typo is having 'tmp', because that variable is unnecessary > >> > and "*data = le32_to_cpu(tmp);" is wrong too. > >> > > >> > Now I also see that also usb_read16() is wrong, while usb_read8() (the one that > >> > I had read yesterday) is the only correct function of the three usb_read*(). > >> > > >> > >> Hi, guys! > >> > >> > >> Sorry for breaking your system, Phillip. This code was part of "last > >> minute" changes and yes, it's broken :) > >> > >> I get what Phillip said, because I _should_ read into tmp variable > >> instead of directly to data, but I don't get Fabio's idea, sorry. > > > > Hi Pavel, > > > > I (wrongly?) assumed from the prototype of usb_read32() that u32 *data is in native > > endianness. So, I didn't see the necessity of using _le32 tmp and then convert that tmp > > with le32_to_cpu(). > > > > I simply thought that data could be passed to usbctrl_vendorreq as it-is. > > > >> Data from chip comes in little-endian, so we _should_ convert it to > >> cpu's endian. Temp variable is needed to make smatch and all other > >> static anylis tools happy about this code. > > > > Now that you explained that "Data from chip comes in little-endian", obviously > > I must agree with you that the code needs tmp and that tmp must be > > swapped by le32_to_cpu(), ahead of assigning it to *data. > > > > Just a curiosity... Since I was not able to see that *data is returned in little endian, > > can you please point me where in the code you found out that it is? There must > > be some place in the code that I'm unable to find and see that *data is LE. > > > > Thanks in advance, > > > > Fabio > > Hi, Fabio! > > previous usb_read16() realization, which is 100% right: > > > static u16 usb_read16(struct intf_hdl *pintfhdl, u32 addr) > { > u8 requesttype; > u16 wvalue; > u16 len; > __le32 data; > > requesttype = 0x01;/* read_in */ > wvalue = (u16)(addr & 0x0000ffff); > len = 2; > usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype); > > return (u16)(le32_to_cpu(data) & 0xffff); > } > > > Bases on this code, I think, it's oblivious, that data comes in > little-endian. That's why I leaved temp variable for casting le32 to > cpu's endianess. > > I could just read into u{16,32} * and then make smth like > > *data = le32_to_cpu(*data) > > but static analysis tools will complain about wrong data type passed to > le32_to_cpu() > > + Phillip tested fixed v2 version and it worked well for him. I guess, > Phillip was able to spot weird driver behavior, if this cast is wrong. > > > > > With regards, > Pavel Skripkin In my mind we can't necessarily assume we are running on a little endian CPU, even if we probably are for practical purposes. That's why my fix looked how it did, but I'm happy to be corrected :-) Also, I can see Dan has looked at the code with suggestions as well. I know you have published v3 - sorry, not had time to review/test it yet. Regards, Phil