linux-kernel - Re: [PATCH 4.9 27/33] futex: Remove duplicated code and fix undefined behaviour

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Date:   Fri, 18 May 2018 10:30:24 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Russell King <rmk+kernel@...linux.org.uk>,
        "Darren Hart (VMware)" <dvhart@...radead.org>,
        linux-mips@...ux-mips.org, Rich Felker <dalias@...c.org>,
        linux-ia64@...r.kernel.org, linux-sh@...r.kernel.org,
        peterz@...radead.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Max Filippov <jcmvbkbc@...il.com>,
        Paul Mackerras <paulus@...ba.org>, sparclinux@...r.kernel.org,
        Jonas Bonn <jonas@...thpole.se>, linux-s390@...r.kernel.org,
        linux-arch@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        linux-hexagon@...r.kernel.org, Helge Deller <deller@....de>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Matt Turner <mattst88@...il.com>,
        linux-snps-arc@...ts.infradead.org,
        Fenghua Yu <fenghua.yu@...el.com>,
        Arnd Bergmann <arnd@...db.de>, linux-xtensa@...ux-xtensa.org,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        openrisc@...ts.librecores.org,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Stafford Horne <shorne@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Richard Henderson <rth@...ddle.net>,
        Chris Zankel <chris@...kel.net>,
        Michal Simek <monstr@...str.eu>,
        Tony Luck <tony.luck@...el.com>, linux-parisc@...r.kernel.org,
        Vineet Gupta <vgupta@...opsys.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Richard Kuo <rkuo@...eaurora.org>, linux-alpha@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        linuxppc-dev@...ts.ozlabs.org,
        "David S. Miller" <davem@...emloft.net>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: Re: [PATCH 4.9 27/33] futex: Remove duplicated code and fix undefined
 behaviour

On 05/18/2018, 10:16 AM, Greg Kroah-Hartman wrote:
> 4.9-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Jiri Slaby <jslaby@...e.cz>
> 
> commit 30d6e0a4190d37740e9447e4e4815f06992dd8c3 upstream.
...
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -1458,6 +1458,45 @@ out:
>  	return ret;
>  }
>  
> +static int futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
> +{
> +	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);

12 is wrong here – wherever you apply this, you need also a follow-up fix:
commit d70ef22892ed6c066e51e118b225923c9b74af34
Author: Jiri Slaby <jslaby@...e.cz>
Date:   Thu Nov 30 15:35:44 2017 +0100

    futex: futex_wake_op, fix sign_extend32 sign bits

thanks,
-- 
js
suse labs