linux-kernel - [PATCH] x86/sgx: Do not limit EAUG'd pages by pre-initialization policy

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Message-Id: <20220304011636.327511-1-jarkko@kernel.org>
Date:   Fri,  4 Mar 2022 03:16:35 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     linux-sgx@...r.kernel.org
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Nathaniel McCallum <nathaniel@...fian.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        "H. Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
        64-BIT))
Subject: [PATCH] x86/sgx: Do not limit EAUG'd pages by pre-initialization policy

Pre-initialization policy is meant for EADD'd pages because they are
part of the enclave identity. It's a good practice to not let touch the
permissions after initialization, and does provide guarantees to e.g.
LSM's about the enclave.

For EAUG'd pages it should be sufficient to let mmap(), mprotect() and
SGX opcodes to control the permissions. Thus effectively disable
pre-initialization policy by setting vm_max_prot_bit and
vm_run_prot_bits to RWX.

Cc: Reinette Chatre <reinette.chatre@...el.com>
Cc: Nathaniel McCallum <nathaniel@...fian.com>
Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
---
 arch/x86/kernel/cpu/sgx/encl.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 5fe7189eac9d..17feb6fa5578 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -200,13 +200,7 @@ static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
 	encl_page->desc = addr;
 	encl_page->encl = encl;
 
-	/*
-	 * Adding a regular page that is architecturally allowed to only
-	 * be created with RW permissions.
-	 * TBD: Interface with user space policy to support max permissions
-	 * of RWX.
-	 */
-	prot = PROT_READ | PROT_WRITE;
+	prot = PROT_READ | PROT_WRITE | PROT_EXEC;
 	encl_page->vm_run_prot_bits = calc_vm_prot_bits(prot, 0);
 	encl_page->vm_max_prot_bits = encl_page->vm_run_prot_bits;
 
-- 
2.35.1