From: Jarkko Sakkinen <jarkko@kernel.org>
To: Reinette Chatre <reinette.chatre@intel.com>,
tony.luck@intel.com, dave.hansen@linux.intel.com,
tglx@linutronix.de, bp@alien8.de, luto@kernel.org,
mingo@redhat.com, linux-sgx@vger.kernel.org, x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] x86/sgx: Add poison handling to reclaimer
Date: Thu, 20 Jan 2022 15:09:03 +0200 [thread overview]
Message-ID: <3bfe66204ee84a0bbccaf7cd20af0d8300fb9f26.camel@kernel.org> (raw)
In-Reply-To: <be5af586f667c7bcb8ef01286ce75675de5d100f.1642630582.git.reinette.chatre@intel.com>
On Wed, 2022-01-19 at 14:23 -0800, Reinette Chatre wrote:
> The SGX reclaimer code lacks page poison handling in its main
> free path. This can lead to avoidable machine checks if a
> poisoned page is freed and reallocated instead of being
> isolated.
>
> A troublesome scenario is:
> 1. Machine check (#MC) occurs (asynchronous, !MF_ACTION_REQUIRED)
> 2. arch_memory_failure() is eventually called
> 3. (SGX) page->poison set to 1
> 4. Page is reclaimed
> 5. Page added to normal free lists by sgx_reclaim_pages()
> ^ This is the bug (poison pages should be isolated on the
> sgx_poison_page_list instead)
> 6. Page is reallocated by some innocent enclave, a second
> (synchronous)
> in-kernel #MC is induced, probably during EADD instruction.
> ^ This is the fallout from the bug
>
> (6) is unfortunate and can be avoided by replacing the open coded
> enclave page freeing code in the reclaimer with sgx_free_epc_page()
> to obtain support for poison page handling that includes placing the
> poisoned page on the correct list.
>
> Fixes: d6d261bded8a ("x86/sgx: Add new sgx_epc_page flag bit to mark
> free pages")
> Fixes: 992801ae9243 ("x86/sgx: Initial poison handling for dirty and
> free pages")
Same comment as for the first version: remove the first fixes tag.
BR, Jarkko
next prev parent reply other threads:[~2022-01-20 13:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-19 22:23 [PATCH V2] x86/sgx: Add poison handling to reclaimer Reinette Chatre
2022-01-20 13:09 ` Jarkko Sakkinen [this message]
2022-01-20 18:20 ` Reinette Chatre
2022-01-22 23:27 ` Jarkko Sakkinen
2022-01-22 23:28 ` Jarkko Sakkinen
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