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From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>,
	Dmitry Safonov <dsafonov@virtuozzo.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>, X86 ML <x86@kernel.org>,
	Oleg Nesterov <oleg@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [RFC 0/3] Put vdso in ramfs-like filesystem (vdsofs)
Date: Tue, 20 Sep 2016 18:17:13 -0700	[thread overview]
Message-ID: <9f45c6d8-df97-6135-a771-d800e73b2fdc@zytor.com> (raw)
In-Reply-To: <6de39359-511e-1ce9-9201-85bd3425a05d@zytor.com>

On 09/20/16 18:07, H. Peter Anvin wrote:
> 
>>  - vvar is highly magical.  IMO letting it get mapped with VM_MAYWRITE
>> is asking for trouble, as anything that writes it will COW it, leading
>> to strange malfunctions.
>>

The vvar page obviously needs to be mapped MAP_SHARED, and the
underlying file needs to reject writes.  A solution where this area
doesn't end up MAP_SHARED is obviously defective.

As far as keeping the user from doing really stupid things... they can
map a RAM page over the vvar area and there is nothing the kernel really
can do to keep them from doing something like that without doing things
that are probably way worse than the disease.  At least it will be
obvious looking at the mapping file what is going on.

	-hpa

  reply	other threads:[~2016-09-21  1:18 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-25 15:21 Dmitry Safonov
2016-08-25 15:21 ` [RFC 1/3] x86/vdso: create vdso file, use it for mapping Dmitry Safonov
2016-08-25 19:49   ` Dmitry Safonov
2016-08-25 20:05     ` Dmitry Safonov
2016-08-28 20:14   ` Cyrill Gorcunov
2016-08-29  9:18     ` Dmitry Safonov
2016-08-29  9:28   ` Andy Lutomirski
2016-08-29  9:50     ` Dmitry Safonov
2016-08-30 14:58       ` Andy Lutomirski
2016-09-03  0:08     ` Al Viro
2016-08-30 14:33   ` Oleg Nesterov
2016-08-30 14:53     ` Dmitry Safonov
2016-09-03  0:13     ` Al Viro
2016-09-03  0:20   ` Al Viro
2016-09-03  7:32     ` Dmitry Safonov
2016-08-25 15:21 ` [RFC 2/3] uprobe: drop isdigit() check in create_trace_uprobe Dmitry Safonov
2016-08-29 22:58   ` Steven Rostedt
2016-08-29 22:59     ` Steven Rostedt
2016-08-29 23:01       ` Dmitry Safonov
2016-08-30 14:37       ` Oleg Nesterov
2016-08-30 21:15         ` Steven Rostedt
2016-08-31 12:07           ` Oleg Nesterov
2016-08-30 14:57     ` Srikar Dronamraju
2016-08-25 15:21 ` [RFC 3/3] uprobe: add vdso support Dmitry Safonov
2016-08-25 20:49 ` [RFC 0/3] Put vdso in ramfs-like filesystem (vdsofs) H. Peter Anvin
2016-08-25 22:53   ` Dmitry Safonov
2016-08-25 23:00     ` H. Peter Anvin
2016-08-26 11:16       ` Dmitry Safonov
2016-08-26 14:32         ` Andy Lutomirski
2016-08-26 14:42           ` Dmitry Safonov
2016-08-26 14:44             ` Dmitry Safonov
2016-09-21  0:22     ` H. Peter Anvin
2016-09-21  0:32       ` H. Peter Anvin
2016-09-21  0:54         ` Andy Lutomirski
2016-09-21  1:07           ` H. Peter Anvin
2016-09-21  1:17             ` H. Peter Anvin [this message]
2016-09-21  6:39               ` Andy Lutomirski

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