From: Pavel Machek <pavel@ucw.cz>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>,
Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
linux-arch@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
Greg KH <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Elena Reshetova <elena.reshetova@intel.com>,
Alan Cox <alan@linux.intel.com>,
Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [RFC PATCH] asm/generic: introduce if_nospec and nospec_barrier
Date: Fri, 5 Jan 2018 00:33:00 +0100 [thread overview]
Message-ID: <20180104233259.GA24680@amd> (raw)
In-Reply-To: <CAPcyv4gVq=F-+8YX6ALUiL61MtOVtDzPrEo18WVsFodZ1YY20A@mail.gmail.com>
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Hi!
> > What did it leak? Nothing. Attacker had to know
> > array+attacker_controlled_index, and he now knows
> > (array+attacker_controlled_index)%CACHELINE_SIZE.
> >
> > With (void) array2[val];, the attack gets interesting -- I now know
> > *(array+attacker_controlled_index) % CACHELINE_SIZE ... allowing me to
> > get information from arbitrary place in memory -- which is useful for
> > .. reading ssh keys, for example.
>
> Right, but how far away from "val = array[attacker_controlled_index];"
> in the instruction stream do you need to look before you're
> comfortable there's no 'val' dependent reads in the speculation window
> on all possible architectures. Until we have variable annotations and
> compiler help my guess is that static analysis has an easier time
> pointing us to the first potentially bad speculative access.
Well, you are already scanning for if (attacker_controlled_index <
limit) .... array[attacker_controlled_index] and those can already be
far away from each other....
Anyway, likely in the end human should be creating the patch, and if
there's no array2[val], we do not need the patch after all.
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2018-01-04 23:33 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-03 22:38 [RFC PATCH 0/4] API for inhibiting speculative arbitrary read primitives Mark Rutland
2018-01-03 22:38 ` [RFC PATCH 1/4] asm-generic/barrier: add generic nospec helpers Mark Rutland
2018-01-04 12:00 ` Mark Rutland
2018-01-05 4:21 ` Dan Williams
2018-01-05 9:15 ` Mark Rutland
2018-01-03 22:38 ` [RFC PATCH 2/4] Documentation: document " Mark Rutland
2018-01-03 22:38 ` [RFC PATCH 3/4] arm64: implement nospec_{load,ptr}() Mark Rutland
2018-01-03 22:38 ` [RFC PATCH 4/4] bpf: inhibit speculated out-of-bounds pointers Mark Rutland
2018-01-03 23:45 ` Peter Zijlstra
2018-01-04 10:59 ` Mark Rutland
2018-01-04 0:15 ` [RFC PATCH] asm/generic: introduce if_nospec and nospec_barrier Dan Williams
2018-01-04 0:39 ` Linus Torvalds
2018-01-04 1:07 ` Alan Cox
2018-01-04 1:13 ` Dan Williams
2018-01-04 6:28 ` Julia Lawall
2018-01-04 17:58 ` Dan Williams
2018-01-04 19:26 ` Pavel Machek
2018-01-04 21:43 ` Dan Williams
2018-01-04 22:20 ` Linus Torvalds
2018-01-04 22:23 ` Linus Torvalds
2018-01-04 22:55 ` Alan Cox
2018-01-04 23:06 ` Linus Torvalds
2018-01-04 23:11 ` Alan Cox
2018-01-05 0:24 ` Dan Williams
2018-01-04 22:44 ` Pavel Machek
2018-01-04 23:12 ` Dan Williams
2018-01-04 23:21 ` Alan Cox
2018-01-04 23:33 ` Pavel Machek [this message]
2018-01-05 8:11 ` Julia Lawall
2018-01-04 1:27 ` Jiri Kosina
2018-01-04 1:41 ` Alan Cox
2018-01-04 1:47 ` Jiri Kosina
2018-01-04 19:39 ` Pavel Machek
2018-01-04 20:32 ` Alan Cox
2018-01-04 20:39 ` Jiri Kosina
2018-01-04 21:23 ` Alan Cox
2018-01-04 21:48 ` Pavel Machek
2018-01-04 1:51 ` Dan Williams
2018-01-04 1:54 ` Linus Torvalds
2018-01-04 3:10 ` Williams, Dan J
2018-01-04 4:44 ` Al Viro
2018-01-04 5:44 ` Dan Williams
2018-01-04 5:49 ` Dave Hansen
2018-01-04 5:50 ` Al Viro
2018-01-04 5:55 ` Al Viro
2018-01-04 6:42 ` Dan Williams
2018-01-04 5:01 ` Eric W. Biederman
2018-01-04 5:01 ` Eric W. Biederman
2018-01-04 6:32 ` Dan Williams
2018-01-04 14:54 ` Eric W. Biederman
2018-01-04 14:54 ` Eric W. Biederman
2018-01-04 16:39 ` Mark Rutland
2018-01-04 20:56 ` Pavel Machek
2018-01-04 11:47 ` Mark Rutland
2018-01-04 11:47 ` Mark Rutland
2018-01-04 11:47 ` Mark Rutland
2018-01-04 22:09 ` Dan Williams
2018-01-05 14:40 ` Mark Rutland
2018-01-05 16:44 ` Dan Williams
2018-01-05 18:05 ` Dan Williams
2018-01-04 1:59 ` Jiri Kosina
2018-01-04 2:15 ` Alan Cox
2018-01-04 3:12 ` Alexei Starovoitov
2018-01-04 9:16 ` Reshetova, Elena
2018-01-04 20:40 ` Pavel Machek
-- strict thread matches above, loose matches on Subject: below --
2018-01-05 10:33 Alexey Dobriyan
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