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From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Benjamin Gray" <bgray@linux.ibm.com>, <linuxppc-dev@lists.ozlabs.org>
Cc: linux-hardening@vger.kernel.org, ajd@linux.ibm.com,
	cmr@bluescreens.de, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 04/13] powerpc/dexcr: Support userspace ROP protection
Date: Tue, 21 Mar 2023 14:51:20 +1000	[thread overview]
Message-ID: <CRBSHXMZX79O.ESN0S8V6M644@bobo> (raw)
In-Reply-To: <eb19afda911f4868ec6ff194738afcfe7050d5c1.camel@linux.ibm.com>

On Tue Mar 7, 2023 at 3:37 PM AEST, Benjamin Gray wrote:
> On Tue, 2023-03-07 at 15:05 +1000, Nicholas Piggin wrote:
> > I think it is not quite per-process? I don't actually know how the
> > user
> > toolchain side is put together, but I'm thinking we can not give it a
> > new
> > salt on fork(), but we could on exec(). I think we could actually
> > give
> > each thread their own salt within a process too, right?
>
> Yeah, the error case is we return further than we called in a given
> execution context. A forked child may return after the fork, meaning it
> needs the same key as the parent for the hashchk to work. Exec can get
> a new key because we can't return with any existing hashes. I haven't
> seen enough of kernel thread support to know if/how we can give threads
> their own key. I believe they go through the fork() call that copies
> the parent key currently.

Could look at possibly doing per-thread keys afterward but what you're
doing makes sense so no problem.

Thanks,
Nick

  reply	other threads:[~2023-03-21  4:52 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-28  2:44 [RFC PATCH 00/13] Add DEXCR support Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 01/13] powerpc/book3s: Add missing <linux/sched.h> include Benjamin Gray
2023-03-07  4:28   ` Nicholas Piggin
2022-11-28  2:44 ` [RFC PATCH 02/13] powerpc: Add initial Dynamic Execution Control Register (DEXCR) support Benjamin Gray
2023-03-07  4:45   ` Nicholas Piggin
2023-03-09 23:46     ` Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 03/13] powerpc/dexcr: Handle hashchk exception Benjamin Gray
2022-11-29 10:39   ` Nicholas Piggin
2022-11-29 22:04     ` Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 04/13] powerpc/dexcr: Support userspace ROP protection Benjamin Gray
2023-03-07  5:05   ` Nicholas Piggin
2023-03-07  5:37     ` Benjamin Gray
2023-03-21  4:51       ` Nicholas Piggin [this message]
2022-11-28  2:44 ` [RFC PATCH 05/13] prctl: Define PowerPC DEXCR interface Benjamin Gray
2023-03-07  5:07   ` Nicholas Piggin
2022-11-28  2:44 ` [RFC PATCH 06/13] powerpc/dexcr: Add prctl implementation Benjamin Gray
2023-03-07  5:12   ` Nicholas Piggin
2022-11-28  2:44 ` [RFC PATCH 07/13] powerpc/dexcr: Add sysctl entry for SBHE system override Benjamin Gray
2023-03-07  5:30   ` Nicholas Piggin
2023-03-07  5:58     ` Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 08/13] powerpc/dexcr: Add enforced userspace ROP protection config Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 09/13] selftests/powerpc: Add more utility macros Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 10/13] selftests/powerpc: Add hashst/hashchk test Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 11/13] selftests/powerpc: Add DEXCR prctl, sysctl interface test Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 12/13] selftests/powerpc: Add DEXCR status utility lsdexcr Benjamin Gray
2022-11-28  2:44 ` [RFC PATCH 13/13] Documentation: Document PowerPC kernel DEXCR interface Benjamin Gray
2023-03-07  5:40   ` Nicholas Piggin
2023-03-07  5:52     ` Benjamin Gray
2022-11-28  4:05 ` [RFC PATCH 00/13] Add DEXCR support Russell Currey

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