linux-kernel - Re: [PATCH v8 07/10] x86, mpx: decode MPX instruction to get bound violation information

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54134464.1010809@zytor.com>
Date:	Fri, 12 Sep 2014 12:07:16 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Dave Hansen <dave.hansen@...el.com>,
	Qiaowei Ren <qiaowei.ren@...el.com>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 07/10] x86, mpx: decode MPX instruction to get bound
 violation information

On 09/12/2014 10:52 AM, Thomas Gleixner wrote:
> 
> Well, I did not see the trainwreck which tried to use the generic
> decoder, but as I explained in the other mail, there is no reason not
> to use it and I can't see any complexity in retrieving the data beyond
> calling insn_get_length(insn);
> 

Looking at how complex the state machine ended up being, it probably was
the wrong direction.  It is safe to copy_from_user() 15 bytes, decode
what we get (which may be less than 15 bytes) and then verify with
insn_get_length() that what we decoded is actually what we copied if the
copy_from_user() length is < 15.

My intent was to explore a state machine limited to the restricted "mib"
encodings that are valid for BNDSTX and BNDLDX only, but in the end it
really doesn't make enough difference that it is worth messing with, I
don't think.

	-hpa

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/