From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: "Rick P. Edgecombe" <rick.p.edgecombe@intel.com>,
Deepak Gupta <debug@rivosinc.com>,
Szabolcs Nagy <Szabolcs.Nagy@arm.com>,
"H.J. Lu" <hjl.tools@gmail.com>,
Florian Weimer <fweimer@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
Christian Brauner <brauner@kernel.org>,
Shuah Khan <shuah@kernel.org>,
linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
jannh@google.com, Andrew Morton <akpm@linux-foundation.org>,
Yury Khrustalev <yury.khrustalev@arm.com>,
Wilco Dijkstra <wilco.dijkstra@arm.com>,
linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org,
Kees Cook <kees@kernel.org>
Subject: Re: [PATCH v20 4/8] fork: Add shadow stack support to clone3()
Date: Wed, 3 Sep 2025 16:34:05 +0100 [thread overview]
Message-ID: <aLhf7XdOO99IyRfA@arm.com> (raw)
In-Reply-To: <734e4c2c-a478-4019-86f7-4965c2b042e1@sirena.org.uk>
On Wed, Sep 03, 2025 at 11:01:05AM +0100, Mark Brown wrote:
> On Tue, Sep 02, 2025 at 10:02:07PM +0100, Catalin Marinas wrote:
> > On Tue, Sep 02, 2025 at 11:21:48AM +0100, Mark Brown wrote:
> > > + mmap_read_lock(mm);
> > > +
> > > + addr = untagged_addr_remote(mm, args->shadow_stack_token);
> > > + page = get_user_page_vma_remote(mm, addr, FOLL_FORCE | FOLL_WRITE,
> > > + &vma);
>
> > However, I wonder whether it makes sense to use the remote mm access
> > here at all. Does this code ever run without CLONE_VM? If not, this is
> > all done within the current mm context.
>
> Yes, userspace can select if it wants CLONE_VM or not so we should
> handle that case. We discussed this on prior versions and we felt that
> while we couldn't immediately see the use case for !CLONE_VM there
> wasn't a good reason to restrict the creativity of userspace developers,
> and given that you can specify the regular stack in these cases it seems
> logical that you'd also be able to specify the shadow stack.
Yeah. Not sure it makes much sense in practice but if we allow a new
stack without CLONE_VM, we should also allow a shadow stack. Thanks for
the clarification.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
next prev parent reply other threads:[~2025-09-03 15:34 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-02 10:21 [PATCH v20 0/8] fork: Support shadow stacks in clone3() Mark Brown
2025-09-02 10:21 ` [PATCH v20 1/8] arm64/gcs: Return a success value from gcs_alloc_thread_stack() Mark Brown
2025-09-02 10:21 ` [PATCH v20 2/8] Documentation: userspace-api: Add shadow stack API documentation Mark Brown
2025-09-02 10:21 ` [PATCH v20 3/8] selftests: Provide helper header for shadow stack testing Mark Brown
2025-09-02 10:21 ` [PATCH v20 4/8] fork: Add shadow stack support to clone3() Mark Brown
2025-09-02 21:02 ` Catalin Marinas
2025-09-03 10:01 ` Mark Brown
2025-09-03 15:34 ` Catalin Marinas [this message]
2025-09-05 15:21 ` Christian Brauner
2025-09-05 15:43 ` Mark Brown
2025-09-05 15:53 ` Edgecombe, Rick P
2025-09-05 16:00 ` Kees Cook
2025-09-05 16:02 ` Mark Brown
2025-09-02 10:21 ` [PATCH v20 5/8] selftests/clone3: Remove redundant flushes of output streams Mark Brown
2025-09-02 10:21 ` [PATCH v20 6/8] selftests/clone3: Factor more of main loop into test_clone3() Mark Brown
2025-09-02 10:21 ` [PATCH v20 7/8] selftests/clone3: Allow tests to flag if -E2BIG is a valid error code Mark Brown
2025-09-02 10:21 ` [PATCH v20 8/8] selftests/clone3: Test shadow stack support Mark Brown
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