linux-kernel - [PATCH V3 2/5] x86/sgx: Mark PCMD page as dirty when modifying contents

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Date:   Thu, 12 May 2022 14:50:58 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     dave.hansen@...ux.intel.com, jarkko@...nel.org, tglx@...utronix.de,
        bp@...en8.de, luto@...nel.org, mingo@...hat.com,
        linux-sgx@...r.kernel.org, x86@...nel.org
Cc:     haitao.huang@...el.com, hpa@...or.com,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH V3 2/5] x86/sgx: Mark PCMD page as dirty when modifying contents

Recent commit 08999b2489b4 ("x86/sgx: Free backing memory
after faulting the enclave page") expanded __sgx_encl_eldu()
to clear an enclave page's PCMD (Paging Crypto MetaData)
from the PCMD page in the backing store after the enclave
page is restored to the enclave.

Since the PCMD page in the backing store is modified the page
should be marked as dirty to ensure the modified data is retained.

Cc: stable@...r.kernel.org
Fixes: 08999b2489b4 ("x86/sgx: Free backing memory after faulting the enclave page")
Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
Tested-by: Haitao Huang <haitao.huang@...el.com>
Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
---
Changes since V2:
- Set page as dirty after receiving data, not before. (Dave)
- Add Jarkko's Reviewed-by tag.
- Add Haitao's Tested-by tag.

Changes since RFC v1:
- Do not set dirty bit on enclave page since it is not being
  written to and always will be discarded.  (Dave)

 arch/x86/kernel/cpu/sgx/encl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 398695a20605..5104a428b72c 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -84,6 +84,7 @@ static int __sgx_encl_eldu(struct sgx_encl_page *encl_page,
 	}
 
 	memset(pcmd_page + b.pcmd_offset, 0, sizeof(struct sgx_pcmd));
+	set_page_dirty(b.pcmd);
 
 	/*
 	 * The area for the PCMD in the page was zeroed above.  Check if the
-- 
2.25.1