From: David Laight <David.Laight@ACULAB.COM>
To: 'Andy Lutomirski' <luto@kernel.org>,
Elena Reshetova <elena.reshetova@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
"Perla, Enrico" <enrico.perla@intel.com>,
"Ingo Molnar" <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Greg KH <gregkh@linuxfoundation.org>
Subject: RE: [RFC PATCH] x86/entry/64: randomize kernel stack offset upon syscall
Date: Wed, 20 Mar 2019 11:12:07 +0000 [thread overview]
Message-ID: <30998bcd55a34ed38b681f9bb3e3fb87@AcuMS.aculab.com> (raw)
In-Reply-To: <CALCETrUxhzHyUQCAjPQcPNWwAw5UTxUX4ZaeGxpbf9VSCDdcPg@mail.gmail.com>
From: Andy Lutomirski
> Sent: 18 March 2019 20:16
...
> > As a result this patch introduces 8 bits of randomness
> > (bits 4 - 11 are randomized, bits 0-3 must be zero due to stack alignment)
> > after pt_regs location on the thread stack.
> > The amount of randomness can be adjusted based on how much of the
> > stack space we wish/can trade for security.
>
> Why do you need four zero bits at the bottom? x86_64 Linux only
> maintains 8 byte stack alignment.
ISTR that the gcc developers arbitrarily changed the alignment
a few years ago.
If the stack is only 8 byte aligned and you allocate a variable that
requires 16 byte alignment you need gcc to generate the extra stack
frame to align the stack.
I don't remember seeing the relevant gcc options on the linux
gcc command lines.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2019-03-20 11:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-18 9:41 [RFC PATCH] x86/entry/64: randomize kernel stack offset upon syscall Elena Reshetova
2019-03-18 20:15 ` Andy Lutomirski
2019-03-18 21:07 ` Kees Cook
2019-03-26 10:35 ` Reshetova, Elena
2019-03-27 4:31 ` Andy Lutomirski
2019-03-28 15:45 ` Kees Cook
2019-03-28 16:29 ` Andy Lutomirski
2019-03-28 16:47 ` Kees Cook
2019-03-29 7:50 ` Reshetova, Elena
2019-03-18 23:31 ` Josh Poimboeuf
2019-03-20 12:10 ` Reshetova, Elena
2019-03-20 11:12 ` David Laight [this message]
2019-03-20 14:51 ` Andy Lutomirski
2019-03-20 12:04 ` Reshetova, Elena
2019-03-20 7:27 Elena Reshetova
2019-03-20 7:29 ` Reshetova, Elena
2019-03-29 8:13 Elena Reshetova
2019-04-03 21:17 ` Kees Cook
2019-04-04 11:41 ` Reshetova, Elena
2019-04-04 17:03 ` Kees Cook
2019-04-05 10:14 ` Reshetova, Elena
2019-04-05 13:14 ` Andy Lutomirski
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