From: Pekka Enberg <penberg@kernel.org>
To: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Matt Mackall <mpm@selenic.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Dave Hansen <dave@linux.vnet.ibm.com>,
Theodore Tso <tytso@mit.edu>,
cl@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] Make /proc/slabinfo 0400
Date: Fri, 4 Mar 2011 22:56:15 +0200 [thread overview]
Message-ID: <AANLkTik6tAfaSr3wxdQ1u_Hd326TmNZe0-FQc3NuYMKN@mail.gmail.com> (raw)
In-Reply-To: <1299271377.2071.1406.camel@dan>
On Fri, 2011-03-04 at 14:31 -0600, Matt Mackall wrote:
>> On Fri, 2011-03-04 at 22:02 +0200, Pekka Enberg wrote:
>> > On Fri, Mar 4, 2011 at 8:14 PM, Matt Mackall <mpm@selenic.com> wrote:
>> > >> Of course, as you say, '/proc/meminfo' still does give you the trigger
>> > >> for "oh, now somebody actually allocated a new page". That's totally
>> > >> independent of slabinfo, though (and knowing the number of active
>> > >> slabs would neither help nor hurt somebody who uses meminfo - you
>> > >> might as well allocate new sockets in a loop, and use _only_ meminfo
>> > >> to see when that allocated a new page).
>> > >
>> > > I think lying to the user is much worse than changing the permissions.
>> > > The cost of the resulting confusion is WAY higher.
>> >
>> > Yeah, maybe. I've attached a proof of concept patch that attempts to
>> > randomize object layout in individual slabs. I'm don't completely
>> > understand the attack vector so I don't make any claims if the patch
>> > helps or not.
>>
>> In general, the attack relies on getting an object A (vulnerable to
>> overrun) immediately beneath an object B (that can be exploited when
>> overrun).
>>
>> I'm not sure how much randomization helps, though. Allocate 1000 objects
>> of type B, deallocate the 800th, then allocate an object of type A. It's
>> almost certainly next to a B.
On Fri, Mar 4, 2011 at 10:42 PM, Dan Rosenberg <drosenberg@vsecurity.com> wrote:
> On second thought, this does pose a problem. Even if you don't know how
> full the most recent slab is or where free vs. used chunks are within
> it, if you can guarantee that you filled an entire previous slab with
> your objects and then free and reallocate one of them, then you can
> still win.
Guys, I still don't get it, sorry.
Why can you still win? With my patch, reallocation shouldn't matter;
the freelist randomization ought to make it less likely for *any* two
allocated objects to be adjacent.
Pekka
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-03-04 20:56 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-03 17:50 Dan Rosenberg
2011-03-03 18:17 ` Dave Hansen
2011-03-03 18:29 ` Dan Rosenberg
2011-03-03 20:58 ` Matt Mackall
2011-03-03 21:16 ` Dan Rosenberg
2011-03-03 21:44 ` Matt Mackall
2011-03-03 22:30 ` Dan Rosenberg
2011-03-03 23:08 ` Matt Mackall
2011-03-04 0:32 ` Dave Hansen
2011-03-04 0:50 ` Theodore Tso
2011-03-04 6:52 ` Pekka Enberg
2011-03-04 17:36 ` Dave Hansen
2011-03-04 17:48 ` Linus Torvalds
2011-03-04 18:14 ` Matt Mackall
2011-03-04 20:02 ` Pekka Enberg
2011-03-04 20:31 ` Matt Mackall
2011-03-04 20:42 ` Dan Rosenberg
2011-03-04 20:56 ` Pekka Enberg [this message]
2011-03-04 21:08 ` Dan Rosenberg
2011-03-04 21:30 ` Pekka Enberg
2011-03-04 21:44 ` Dan Rosenberg
2011-03-04 22:10 ` Pekka Enberg
2011-03-04 22:14 ` Pekka Enberg
2011-03-04 23:02 ` Matt Mackall
2011-03-05 16:25 ` Ted Ts'o
2011-03-06 13:19 ` Alan Cox
2011-03-07 14:56 ` Dan Rosenberg
2011-03-07 16:02 ` Matt Mackall
2011-03-04 20:37 ` Dan Rosenberg
2011-03-04 20:58 ` Pekka Enberg
2011-03-04 21:10 ` Dan Rosenberg
2011-03-06 0:42 ` Jesper Juhl
2011-03-06 0:57 ` Dan Rosenberg
2011-03-06 1:09 ` Matt Mackall
2011-03-06 1:15 ` Jesper Juhl
2011-03-07 16:40 ` Christoph Lameter
2011-03-04 21:12 ` Matt Mackall
2011-03-04 11:58 ` Alan Cox
2011-03-07 14:19 [PATCH] Make /proc/slabinfo 040 George Spelvin
2011-03-07 17:49 ` [PATCH] Make /proc/slabinfo 0400 George Spelvin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=AANLkTik6tAfaSr3wxdQ1u_Hd326TmNZe0-FQc3NuYMKN@mail.gmail.com \
--to=penberg@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=cl@linux-foundation.org \
--cc=dave@linux.vnet.ibm.com \
--cc=drosenberg@vsecurity.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@elte.hu \
--cc=mpm@selenic.com \
--cc=torvalds@linux-foundation.org \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox