linux-kernel - Re: [PATCH V2] posix-timers: Protect posix clock array access against speculation

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Date:   Thu, 15 Feb 2018 18:01:04 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH V2] posix-timers: Protect posix clock array access
 against speculation

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@...utronix.de>
> Cc: stable@...r.kernel.org

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

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