From: Russell Currey <ruscur@russell.cc>
To: Benjamin Gray <bgray@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org
Cc: npiggin@gmail.com
Subject: Re: [PATCH v2 08/12] powerpc/ptrace: Expose HASHKEYR register to ptrace
Date: Mon, 08 May 2023 14:32:36 +1000 [thread overview]
Message-ID: <9aec74cceccb016effceecc01f3ce2bd1744e2cb.camel@russell.cc> (raw)
In-Reply-To: <20230330055040.434133-9-bgray@linux.ibm.com>
On Thu, 2023-03-30 at 16:50 +1100, Benjamin Gray wrote:
> The HASHKEYR register contains a secret per-process key to enable
> unique
> hashes per process. In general it should not be exposed to userspace
> at all and a regular process has no need to know its key.
>
> However, checkpoint restore in userspace (CRIU) functionality
> requires
> that a process be able to set the HASHKEYR of another process,
> otherwise
> existing hashes on the stack would be invalidated by a new random
> key.
>
> Exposing HASHKEYR in this way also makes it appear in core dumps,
> which
> is a security concern. Multiple threads may share a key, for example
> just after a fork() call, where the kernel cannot know if the child
> is
> going to return back along the parent's stack. If such a thread is
> coerced into making a core dump, then the HASHKEYR value will be
> readable and able to be used against all other threads sharing that
> key,
> effectively undoing any protection offered by hashst/hashchk.
>
> Therefore we expose HASHKEYR to ptrace when CONFIG_CHECKPOINT_RESTORE
> is
> enabled, providing a choice of increased security or migratable ROP
> protected processes. This is similar to how ARM exposes its PAC keys.
>
> Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Seems sensible
Reviewed-by: Russell Currey <ruscur@russell.cc>
next prev parent reply other threads:[~2023-05-08 4:33 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-30 5:50 [PATCH v2 00/12] Add static DEXCR support Benjamin Gray
2023-03-30 5:50 ` [PATCH v2 01/12] powerpc/book3s: Add missing <linux/sched.h> include Benjamin Gray
2023-05-08 3:36 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 02/12] powerpc/ptrace: Add missing <linux/regset.h> include Benjamin Gray
2023-05-08 3:39 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 03/12] powerpc/dexcr: Add initial Dynamic Execution Control Register (DEXCR) support Benjamin Gray
2023-05-08 3:44 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 04/12] powerpc/dexcr: Handle hashchk exception Benjamin Gray
2023-05-08 4:00 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 05/12] powerpc/dexcr: Support userspace ROP protection Benjamin Gray
2023-05-08 4:10 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 06/12] powerpc/dexcr: Support custom default DEXCR value Benjamin Gray
2023-05-08 4:24 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 07/12] powerpc/ptrace: Expose DEXCR and HDEXCR registers to ptrace Benjamin Gray
2023-05-08 4:30 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 08/12] powerpc/ptrace: Expose HASHKEYR register " Benjamin Gray
2023-05-08 4:32 ` Russell Currey [this message]
2023-03-30 5:50 ` [PATCH v2 09/12] Documentation: Document PowerPC kernel DEXCR interface Benjamin Gray
2023-05-08 4:40 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 10/12] selftests/powerpc: Add more utility macros Benjamin Gray
2023-05-08 4:43 ` Russell Currey
2023-03-30 5:50 ` [PATCH v2 11/12] selftests/powerpc/dexcr: Add hashst/hashchk test Benjamin Gray
2023-03-30 5:50 ` [PATCH v2 12/12] selftests/powerpc/dexcr: Add DEXCR status utility lsdexcr Benjamin Gray
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