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Date: Thu, 15 Feb 2018 18:01:04 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Dan Williams <dan.j.williams@intel.com>,
	Rasmus Villemoes <rasmus.villemoes@prevas.dk>,
	LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [PATCH V2] posix-timers: Protect posix clock array access
 against speculation
Message-ID: <20180215170104.GC25181@hirez.programming.kicks-ass.net>
References: <alpine.DEB.2.21.1802151424490.1296@nanos.tec.linutronix.de>
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 <alpine.DEB.2.21.1802151550330.1296@nanos.tec.linutronix.de>
 <alpine.DEB.2.21.1802151718320.1296@nanos.tec.linutronix.de>
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On Thu, Feb 15, 2018 at 05:21:55PM +0100, Thomas Gleixner wrote:
> The clockid argument of clockid_to_kclock() comes straight from user space
> via various syscalls and is used as index into the posix_clocks array.
> 
> Protect it against spectre v1 array out of bounds speculation. Remove the
> redundant check for !posix_clock[id] as this is another source for
> speculation and does not provide any advantage over the return
> posix_clock[id] path which returns NULL in that case anyway.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: stable@vger.kernel.org

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

It might also be useful to figure out why the automation didn't flag
this one, its about as trivial as it gets.