From: Mark Brown <broonie@kernel.org>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "Szabolcs.Nagy@arm.com" <Szabolcs.Nagy@arm.com>,
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Subject: Re: [PATCH RFC RFT v2 2/5] fork: Add shadow stack support to clone3()
Date: Thu, 16 Nov 2023 18:41:08 +0000 [thread overview]
Message-ID: <eebf054b-7e0e-4732-8d8c-718073ec32ed@sirena.org.uk> (raw)
In-Reply-To: <9ce63f824b768f9635e55150815ee614fdee1d73.camel@intel.com>
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On Thu, Nov 16, 2023 at 06:11:17PM +0000, Edgecombe, Rick P wrote:
> Now that I've thought about it more, removing the CLONE_VFORK part of
> the logic has several downsides. It is a little extra work to create
> and unmap a shadow stack for an operation that is supposed to be this
> limited fast thing.
It does rather feel like it's defeating the point of the thing.
> It also will change the SSP(let me know if anyone has a general term we
> can use) for the child. So if you have like:
SSP seems fine, we're already using shadow stack here.
> What about a CLONE_NEW_SHSTK for clone3 that forces a new shadow stack?
> So keep the existing logic, but the new flag can override the logic for
> !CLONE_VM and CLONE_VFORK if the caller wants. The behavior of
> shadow_stack_size is then simple. 0 means use default size, !0 means
> use the passed size. No need to overload and tie up args->stack.
That does seem like it cuts through the ambiguous cases. If we go for
that it feels like we should require the flag when specifying a size,
just to be sure that everything is clear. Though having said that we
could just always allocate a shadow stack if a size is specified
regardless of the flags, requiring people who want non-default behaviour
to have some idea what stack size they want. I don't think I have
strong opinons between having the new flag or always allocating a stack
if a size is specified.
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next prev parent reply other threads:[~2023-11-16 18:41 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-14 20:05 [PATCH RFC RFT v2 0/5] fork: Support shadow stacks in clone3() Mark Brown
2023-11-14 20:05 ` [PATCH RFC RFT v2 1/5] mm: Introduce ARCH_HAS_USER_SHADOW_STACK Mark Brown
2023-11-14 23:22 ` Edgecombe, Rick P
2023-11-15 14:55 ` Mark Brown
2023-11-15 15:12 ` David Hildenbrand
2023-11-15 15:36 ` Deepak Gupta
2023-11-14 20:05 ` [PATCH RFC RFT v2 2/5] fork: Add shadow stack support to clone3() Mark Brown
2023-11-15 0:45 ` Edgecombe, Rick P
2023-11-15 12:36 ` Mark Brown
2023-11-15 16:20 ` Szabolcs.Nagy
2023-11-15 18:43 ` Mark Brown
2023-11-16 0:52 ` Edgecombe, Rick P
2023-11-16 10:32 ` Szabolcs.Nagy
2023-11-16 12:33 ` Mark Brown
2023-11-16 13:12 ` Szabolcs.Nagy
2023-11-16 13:55 ` Szabolcs.Nagy
2023-11-16 15:35 ` Mark Brown
2023-11-16 18:11 ` Edgecombe, Rick P
2023-11-16 18:41 ` Mark Brown [this message]
2023-11-17 17:43 ` Edgecombe, Rick P
2023-11-20 16:11 ` Mark Brown
2023-11-16 18:14 ` Mark Brown
2023-11-16 18:33 ` Edgecombe, Rick P
2023-11-17 20:51 ` Deepak Gupta
2023-11-14 20:05 ` [PATCH RFC RFT v2 3/5] selftests/clone3: Factor more of main loop into test_clone3() Mark Brown
2023-11-14 20:05 ` [PATCH RFC RFT v2 4/5] selftests/clone3: Allow tests to flag if -E2BIG is a valid error code Mark Brown
2023-11-14 20:05 ` [PATCH RFC RFT v2 5/5] kselftest/clone3: Test shadow stack support Mark Brown
2023-11-14 23:11 ` Edgecombe, Rick P
2023-11-15 12:53 ` Mark Brown
2023-11-17 18:16 ` Edgecombe, Rick P
2023-11-17 21:12 ` Deepak Gupta
2023-11-20 15:47 ` Mark Brown
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