linux-kernel - Re: [PATCH 1/1] futex: remove duplicated code and fix UB

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Message-ID: <80af8d81-4522-de2d-8289-1ab46565505a@suse.cz>
Date:   Mon, 26 Jun 2017 14:02:31 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>
Cc:     mingo@...hat.com, peterz@...radead.org, dvhart@...radead.org,
        linux-kernel@...r.kernel.org, Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Richard Kuo <rkuo@...eaurora.org>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Michal Simek <monstr@...str.eu>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Stafford Horne <shorne@...il.com>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S. Miller" <davem@...emloft.net>,
        "H. Peter Anvin" <hpa@...or.com>, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Arnd Bergmann <arnd@...db.de>, x86@...nel.org,
        linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-mips@...ux-mips.org, openrisc@...ts.librecores.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
        linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/1] futex: remove duplicated code and fix UB

On 06/23/2017, 09:51 AM, Thomas Gleixner wrote:
> On Wed, 21 Jun 2017, Jiri Slaby wrote:
>> diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
>> index f32b42e8725d..5bb2fd4674e7 100644
>> --- a/arch/arm64/include/asm/futex.h
>> +++ b/arch/arm64/include/asm/futex.h
>> @@ -48,20 +48,10 @@ do {									\
>>  } while (0)
>>  
>>  static inline int
>> -futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
> 
> That unsigned int seems to be a change from the arm64 tree in next. It's
> not upstream and it'll cause a (easy to resolve) conflict.

Ugh, I thought the arm64 is in upstream already. Note that this patch
just takes what is in this arm64 fix and makes it effective for all
architectures. So I will wait with v2 until it merges upstream.

So, Will, will you incorporate Thomas' comments into your arm64 fix?

...

> Yes, we probably can't change that anymore, but at least we should make it
> very explicit and add a comment to that effect.

Something like this or do you want a comment yet?
        unsigned int op =         (encoded_op & 0x70000000) >> 28;
        unsigned int cmp =        (encoded_op & 0x0f000000) >> 24;
        int oparg = sign_extend32((encoded_op & 0x00fff000) >> 12, 12);
        int cmparg = sign_extend32(encoded_op & 0x00000fff, 12);

thanks,
-- 
js
suse labs