[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAGXu5jLMCK6yudcp5kyGpC-CdHdhBFRGkzW84GfOjZPhyV2kOQ@mail.gmail.com>
Date: Sat, 18 Nov 2017 00:20:56 -0800
From: Kees Cook <keescook@...omium.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Patrick McLean <chutzpah@...too.org>, Emese Revfy <re.emese@...il.com>,
Al Viro <viro@...iv.linux.org.uk>, Bruce Fields <bfields@...hat.com>,
"Darrick J. Wong" <darrick.wong@...cle.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux NFS Mailing List <linux-nfs@...r.kernel.org>, stable <stable@...r.kernel.org>,
Thorsten Leemhuis <regressions@...mhuis.info>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [nfsd4] potentially hardware breaking regression in 4.14-rc and 4.13.11
On Fri, Nov 17, 2017 at 9:29 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Fri, Nov 17, 2017 at 9:14 PM, Kees Cook <keescook@...omium.org> wrote:
>>
>> FWIW, myself doing a build at d9e12200852d with and without
>> GCC_PLUGIN_RANDSTRUCT _appears_ to produce identical objdump output
>> where I did spot-checks.
>
> That would probably be a good thing to check anyway - check the
> difference between GCC_PLUGIN_RANDSTRUCT on and off at that commit.
>
> Just do
>
> objdump --disassemble vmlinux > file
>
> and compare the two files for where the differences start occurring.
Yeah, I was just doing that now. Looks like there _is_ something
getting changed just from having the plugin enabled, but it appears
localized. For me, the first non-offset change happens in
lookup_user_key and persists for a while.
-ffffffff813893a7: 0f 85 55 03 00 00 jne
ffffffff81389702 <lookup_user_key+0x3f2>
-ffffffff813893ad: f0 41 ff 06 lock incl (%r14)
-ffffffff813893b1: 83 fb 07 cmp $0x7,%ebx
-ffffffff813893b4: 4c 89 b5 70 ff ff ff mov %r14,-0x90(%rbp)
...
+ffffffff813893a7: 0f 85 35 03 00 00 jne
ffffffff813896e2 <lookup_user_key+0x3d2>
+ffffffff813893ad: 4d 89 f0 mov %r14,%r8
+ffffffff813893b0: f0 41 ff 06 lock incl (%r14)
+ffffffff813893b4: 83 fb 07 cmp $0x7,%ebx
+ffffffff813893b7: 4c 89 b5 70 ff ff ff mov %r14,-0x90(%rbp)
And removing the TYPE_ATTRIBUTES() poking makes the register storage
differences go away, but there's still a 0x40 byte offset delta.
I'll continue looking at this tomorrow.
-Kees
--
Kees Cook
Pixel Security
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
