From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f54.google.com (mail-lf1-f54.google.com [209.85.167.54]) (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 012DD72 for ; Tue, 24 Aug 2021 08:47:15 +0000 (UTC) Received: by mail-lf1-f54.google.com with SMTP id g13so43807752lfj.12 for ; Tue, 24 Aug 2021 01:47:15 -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=l/0DcoU3NR5Hm+Z2+0dYvQke43s7NiVsSxOhSfpWkyE=; b=KItREUdnxeMFcle3E7sljnZ3PpyGaLXWXOR1lbD+JaDUQ7TOO2KpmsV3I+YeXz2RDq IUkircfEpRJ/72D1ETGD2RKXrKXgd10JB+xUOZFqgOaB24/gXCFZ7j4PaxSWrQGjyaeO Pv7VXjFIh6L3buSbrsRCnXtHbw+VspB4TDQHhTAlXXDW8MAji6HnOMbl7nd7y7ERE++m mj/IoaQsEXmYGB0ECXoC+CaPelys7WHzGG/gUbZjwmolyFSq3iMYG7aFAIcxY1qkOAir H+UN4mykEll86s2cs95q0MDcT/s80+5vEYZOU4zR4NKjMS7oDlskTUTb+t46f2WL5tKo NNTQ== 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=l/0DcoU3NR5Hm+Z2+0dYvQke43s7NiVsSxOhSfpWkyE=; b=m+mzRJcxRL6XbWLQOBrXXSF+DtM91rtaT3j4R0O28gQajpN0UG8B2d+343oWtt8gYu zeTOajQlMmfrLH3u8NyjhuAYXBPdsJxsaqgqYl1Vc3/ocC7+OF4qmJ28iQb3R49r49Y3 +9UJ1BPdsDzIPBfa6bcZcoh6p8B/ql5pDD4brBAA2VJkt1Sq5Fv4XQKk7oEj7jzLhrYv rhSB1ZXGGt3fYY/cYbzfTrN/HOR824WDXg+HKwD4N8m718RYEDeofphdLfnJPmKcCu+l n1lcSj7oiJH0eaJVtAkPSjUbq94nkyDAQjEn3r5xCcHl7+KVfrdgAIWOnpRupbR5y4Tz SGGg== X-Gm-Message-State: AOAM5336DBL2J/tq4p+P55UdZmSWPOlrfzDxSOdBN7ybaWJZbzVKDJV1 G5hsHb3TWVa9/S815bdJNHk= X-Google-Smtp-Source: ABdhPJypAbTeZN5vx+Sh2a5uJJ2rXXiMS1W8bm6Usj7WPhEdVnu0MEht7qeSR1Tfn7vKOa3lqADXJA== X-Received: by 2002:a05:6512:2290:: with SMTP id f16mr1315159lfu.525.1629794834129; Tue, 24 Aug 2021 01:47:14 -0700 (PDT) Received: from [192.168.1.11] ([46.235.66.127]) by smtp.gmail.com with ESMTPSA id x2sm1700054ljn.12.2021.08.24.01.47.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Aug 2021 01:47:13 -0700 (PDT) Subject: Re: [PATCH RFC v2 5/6] staging: r8188eu: add error handling of rtw_read32 To: "Fabio M. De Francesco" , Phillip Potter Cc: Larry Finger , Greg KH , Michael Straube , "open list:STAGING SUBSYSTEM" , Linux Kernel Mailing List References: <2424268.2DCLMNk6Lg@localhost.localdomain> <2355365e-d75e-8d1b-aad8-6979b70f33ec@gmail.com> <3419359.n4KOUNuIW1@localhost.localdomain> From: Pavel Skripkin Message-ID: <77da7c63-a5b1-a09d-39ec-32c5485b8eac@gmail.com> Date: Tue, 24 Aug 2021 11:47:12 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <3419359.n4KOUNuIW1@localhost.localdomain> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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