From: Reinette Chatre <reinette.chatre@intel.com>
To: dave.hansen@linux.intel.com, jarkko@kernel.org,
tglx@linutronix.de, bp@alien8.de, luto@kernel.org,
mingo@redhat.com, linux-sgx@vger.kernel.org, x86@kernel.org
Cc: seanjc@google.com, kai.huang@intel.com, cathy.zhang@intel.com,
cedric.xing@intel.com, haitao.huang@intel.com,
mark.shanahan@intel.com, hpa@zytor.com,
linux-kernel@vger.kernel.org
Subject: [PATCH V2 08/32] x86/sgx: x86/sgx: Add sgx_encl_page->vm_run_prot_bits for dynamic permission changes
Date: Mon, 7 Feb 2022 16:45:30 -0800 [thread overview]
Message-ID: <5136c1984544a18aadf17df040dfd8c846a22f18.1644274683.git.reinette.chatre@intel.com> (raw)
In-Reply-To: <cover.1644274683.git.reinette.chatre@intel.com>
Enclave creators declare their enclave page permissions (EPCM
permissions) at the time the pages are added to the enclave. These
page permissions are the vetted permissible accesses of the enclave
pages and stashed off (in struct sgx_encl_page->vm_max_prot_bits)
for later comparison with enclave PTEs and VMAs.
Current permission support assume that EPCM permissions remain static
for the lifetime of the enclave. This is about to change with the
addition of support for SGX2 where the EPCM permissions of enclave
pages belonging to an initialized enclave may change during the
enclave's lifetime.
Support for changing of EPCM permissions should continue to respect
the vetted maximum protection bits maintained in
sgx_encl_page->vm_max_prot_bits. Towards this end, add
sgx_encl_page->vm_run_prot_bits in preparation for support of
enclave page permission changes. sgx_encl_page->vm_run_prot_bits
reflect the active EPCM permissions of an enclave page and are not to
exceed sgx_encl_page->vm_max_prot_bits.
Two permission fields are used: sgx_encl_page->vm_run_prot_bits
reflects the current EPCM permissions and is used to manage the page
table entries while sgx_encl_page->vm_max_prot_bits contains the vetted
maximum protection bits and is used to guide which EPCM permissions
are allowed in the upcoming SGX2 permission changing support (it guides
what values sgx_encl_page->vm_run_prot_bits may have).
Consider this example how sgx_encl_page->vm_max_prot_bits and
sgx_encl_page->vm_run_prot_bits are used:
(1) Add an enclave page with secinfo of RW to an uninitialized enclave:
sgx_encl_page->vm_max_prot_bits = RW
sgx_encl_page->vm_run_prot_bits = RW
At this point RW VMAs would be allowed to access this page and PTEs
would allow write access as guided by
sgx_encl_page->vm_run_prot_bits.
(2) User space invokes SGX2 to change the EPCM permissions to read-only.
This is allowed because sgx_encl_page->vm_max_prot_bits = RW:
sgx_encl_page->vm_max_prot_bits = RW
sgx_encl_page->vm_run_prot_bits = R
At this point only new read-only VMAs would be allowed to access
this page and PTEs would not allow write access as guided
by sgx_encl_page->vm_run_prot_bits.
(3) User space invokes SGX2 to change the EPCM permissions to RX.
This will not be supported by the kernel because
sgx_encl_page->vm_max_prot_bits = RW:
sgx_encl_page->vm_max_prot_bits = RW
sgx_encl_page->vm_run_prot_bits = R
(3) User space invokes SGX2 to change the EPCM permissions to RW.
This will be allowed because sgx_encl_page->vm_max_prot_bits = RW:
sgx_encl_page->vm_max_prot_bits = RW
sgx_encl_page->vm_run_prot_bits = RW
At this point RW VMAs would again be allowed to access this page
and PTEs would allow write access as guided by
sgx_encl_page->vm_run_prot_bits.
struct sgx_encl_page hosting this information is maintained for each
enclave page so the space consumed by the struct is important.
The existing sgx_encl_page->vm_max_prot_bits is already unsigned long
while only using three bits. Transition to a bitfield for the two
members containing protection bits.
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
Changes since V1:
- Add snippet to Documentation/x86/sgx.rst that details the difference
between vm_max_prot_bits and vm_run_prot_bits (Andy and Jarkko).
- Change subject line (Jarkko).
- Refer to actual variables instead of using English rephrasing -
sgx_encl_page->vm_run_prot_bits instead of "runtime
protection bits" (Jarkko).
- Add information in commit message on why two fields are needed
(Jarkko).
Documentation/x86/sgx.rst | 10 ++++++++++
arch/x86/kernel/cpu/sgx/encl.c | 6 +++---
arch/x86/kernel/cpu/sgx/encl.h | 3 ++-
arch/x86/kernel/cpu/sgx/ioctl.c | 6 ++++++
4 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/Documentation/x86/sgx.rst b/Documentation/x86/sgx.rst
index 5659932728a5..9df620b59f83 100644
--- a/Documentation/x86/sgx.rst
+++ b/Documentation/x86/sgx.rst
@@ -99,6 +99,16 @@ The relationships between the different permission masks are:
* PTEs are installed to match the EPCM permissions, but not be more
relaxed than the VMA permissions.
+During runtime the EPCM permissions of enclave pages belonging to an
+initialized enclave can change on systems supporting SGX2. In support
+of these runtime changes the kernel maintains (for each enclave page)
+the most permissive EPCM permission mask allowed by policy as
+the ``vm_max_prot_bits`` of that page. EPCM permissions are not allowed
+to be relaxed beyond ``vm_max_prot_bits``. The kernel also maintains
+the currently active EPCM permissions of an enclave page as its
+``vm_run_prot_bits`` to ensure PTEs and new VMAs respect the active
+EPCM permission values.
+
On systems supporting SGX2 EPCM permissions may change while the
enclave page belongs to a VMA without impacting the VMA permissions.
This means that a running VMA may appear to allow access to an enclave
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 1ba01c75a579..a980d8458949 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -164,7 +164,7 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf)
* exceed the VMA permissions.
*/
vm_prot_bits = vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC);
- page_prot_bits = entry->vm_max_prot_bits & vm_prot_bits;
+ page_prot_bits = entry->vm_run_prot_bits & vm_prot_bits;
/*
* Add VM_SHARED so that PTE is made writable right away if VMA
* and EPCM are writable (no COW in SGX).
@@ -217,7 +217,7 @@ static vm_fault_t sgx_vma_pfn_mkwrite(struct vm_fault *vmf)
goto out;
}
- if (!(entry->vm_max_prot_bits & VM_WRITE))
+ if (!(entry->vm_run_prot_bits & VM_WRITE))
ret = VM_FAULT_SIGBUS;
out:
@@ -280,7 +280,7 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start,
mutex_lock(&encl->lock);
xas_lock(&xas);
xas_for_each(&xas, page, PFN_DOWN(end - 1)) {
- if (~page->vm_max_prot_bits & vm_prot_bits) {
+ if (~page->vm_run_prot_bits & vm_prot_bits) {
ret = -EACCES;
break;
}
diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
index fec43ca65065..dc262d843411 100644
--- a/arch/x86/kernel/cpu/sgx/encl.h
+++ b/arch/x86/kernel/cpu/sgx/encl.h
@@ -27,7 +27,8 @@
struct sgx_encl_page {
unsigned long desc;
- unsigned long vm_max_prot_bits;
+ unsigned long vm_max_prot_bits:8;
+ unsigned long vm_run_prot_bits:8;
struct sgx_epc_page *epc_page;
struct sgx_encl *encl;
struct sgx_va_page *va_page;
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 83df20e3e633..7e0819a89532 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -197,6 +197,12 @@ static struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
/* Calculate maximum of the VM flags for the page. */
encl_page->vm_max_prot_bits = calc_vm_prot_bits(prot, 0);
+ /*
+ * At time of allocation, the runtime protection bits are the same
+ * as the maximum protection bits.
+ */
+ encl_page->vm_run_prot_bits = encl_page->vm_max_prot_bits;
+
return encl_page;
}
--
2.25.1
next prev parent reply other threads:[~2022-02-08 1:07 UTC|newest]
Thread overview: 130+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-08 0:45 [PATCH V2 00/32] x86/sgx and selftests/sgx: Support SGX2 Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 01/32] x86/sgx: Add short descriptions to ENCLS wrappers Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 02/32] x86/sgx: Add wrapper for SGX2 EMODPR function Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 03/32] x86/sgx: Add wrapper for SGX2 EMODT function Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 04/32] x86/sgx: Add wrapper for SGX2 EAUG function Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 05/32] Documentation/x86: Document SGX permission details Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 06/32] x86/sgx: Support VMA permissions more relaxed than enclave permissions Reinette Chatre
2022-03-07 17:10 ` Jarkko Sakkinen
2022-03-07 17:36 ` Reinette Chatre
2022-03-08 8:14 ` Jarkko Sakkinen
2022-03-08 9:06 ` Jarkko Sakkinen
2022-03-08 9:12 ` Jarkko Sakkinen
2022-03-08 16:04 ` Reinette Chatre
2022-03-08 17:00 ` Jarkko Sakkinen
2022-03-08 17:49 ` Reinette Chatre
2022-03-08 18:46 ` Jarkko Sakkinen
2022-03-11 11:06 ` Dr. Greg
2022-02-08 0:45 ` [PATCH V2 07/32] x86/sgx: Add pfn_mkwrite() handler for present PTEs Reinette Chatre
2022-02-08 0:45 ` Reinette Chatre [this message]
2022-03-04 8:55 ` [PATCH V2 08/32] x86/sgx: x86/sgx: Add sgx_encl_page->vm_run_prot_bits for dynamic permission changes Jarkko Sakkinen
2022-03-04 19:19 ` Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 09/32] x86/sgx: Export sgx_encl_ewb_cpumask() Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 10/32] x86/sgx: Rename sgx_encl_ewb_cpumask() as sgx_encl_cpumask() Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 11/32] x86/sgx: Move PTE zap code to new sgx_zap_enclave_ptes() Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 12/32] x86/sgx: Make sgx_ipi_cb() available internally Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 13/32] x86/sgx: Create utility to validate user provided offset and length Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 14/32] x86/sgx: Keep record of SGX page type Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 15/32] x86/sgx: Support relaxing of enclave page permissions Reinette Chatre
2022-03-04 8:59 ` Jarkko Sakkinen
2022-02-08 0:45 ` [PATCH V2 16/32] x86/sgx: Support restricting " Reinette Chatre
2022-02-21 0:49 ` Jarkko Sakkinen
2022-02-22 18:35 ` Reinette Chatre
2022-02-23 15:46 ` Jarkko Sakkinen
2022-02-23 19:55 ` Reinette Chatre
2022-02-28 12:27 ` Jarkko Sakkinen
2022-02-23 19:21 ` Dhanraj, Vijay
2022-02-23 22:42 ` Reinette Chatre
2022-02-28 12:24 ` Jarkko Sakkinen
2022-02-28 13:19 ` Jarkko Sakkinen
2022-02-28 15:16 ` Dave Hansen
2022-02-28 17:44 ` Dhanraj, Vijay
2022-03-01 13:26 ` Jarkko Sakkinen
2022-03-01 13:42 ` Jarkko Sakkinen
2022-03-01 17:48 ` Reinette Chatre
2022-03-02 2:05 ` Jarkko Sakkinen
2022-03-02 2:11 ` Jarkko Sakkinen
2022-03-02 4:03 ` Jarkko Sakkinen
2022-03-02 22:57 ` Reinette Chatre
2022-03-03 16:08 ` Haitao Huang
2022-03-03 21:23 ` Reinette Chatre
2022-03-03 21:44 ` Dave Hansen
2022-03-05 3:19 ` Jarkko Sakkinen
2022-03-06 0:15 ` Jarkko Sakkinen
2022-03-06 0:25 ` Jarkko Sakkinen
2022-03-10 5:43 ` Jarkko Sakkinen
2022-03-10 5:59 ` Jarkko Sakkinen
2022-03-03 23:18 ` Jarkko Sakkinen
2022-03-04 4:03 ` Haitao Huang
2022-03-04 8:30 ` Jarkko Sakkinen
2022-03-04 15:51 ` Haitao Huang
2022-03-05 1:02 ` Jarkko Sakkinen
2022-03-06 14:24 ` Haitao Huang
2022-03-03 23:12 ` Jarkko Sakkinen
2022-03-04 0:48 ` Reinette Chatre
2022-03-10 6:10 ` Jarkko Sakkinen
2022-03-10 18:33 ` Haitao Huang
2022-03-11 12:10 ` Jarkko Sakkinen
2022-03-11 12:16 ` Jarkko Sakkinen
2022-03-11 12:33 ` Jarkko Sakkinen
2022-03-11 17:53 ` Reinette Chatre
2022-03-11 18:11 ` Jarkko Sakkinen
2022-03-11 19:28 ` Reinette Chatre
2022-03-14 3:42 ` Jarkko Sakkinen
2022-03-14 3:45 ` Jarkko Sakkinen
2022-03-14 3:54 ` Jarkko Sakkinen
2022-03-14 15:32 ` Reinette Chatre
2022-03-17 4:30 ` Jarkko Sakkinen
2022-03-17 22:08 ` Reinette Chatre
2022-03-17 22:51 ` Jarkko Sakkinen
2022-03-18 0:11 ` Reinette Chatre
2022-03-20 0:24 ` Jarkko Sakkinen
2022-03-28 23:22 ` Reinette Chatre
2022-03-30 15:00 ` Jarkko Sakkinen
2022-03-30 15:02 ` Jarkko Sakkinen
2022-03-14 2:49 ` Jarkko Sakkinen
2022-03-14 2:50 ` Jarkko Sakkinen
2022-03-14 2:58 ` Jarkko Sakkinen
2022-03-14 15:39 ` Haitao Huang
2022-03-17 4:34 ` Jarkko Sakkinen
2022-03-17 14:42 ` Haitao Huang
2022-03-17 4:37 ` Jarkko Sakkinen
2022-03-17 14:47 ` Haitao Huang
2022-03-17 7:01 ` Jarkko Sakkinen
2022-03-17 7:11 ` Jarkko Sakkinen
2022-03-17 14:28 ` Haitao Huang
2022-03-17 21:50 ` Jarkko Sakkinen
2022-03-17 22:00 ` Jarkko Sakkinen
2022-03-17 22:23 ` Jarkko Sakkinen
2022-02-08 0:45 ` [PATCH V2 17/32] selftests/sgx: Add test for EPCM permission changes Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 18/32] selftests/sgx: Add test for TCS page " Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 19/32] x86/sgx: Support adding of pages to an initialized enclave Reinette Chatre
2022-02-19 11:57 ` Jarkko Sakkinen
2022-02-19 12:01 ` Jarkko Sakkinen
2022-02-20 18:40 ` Jarkko Sakkinen
2022-02-22 19:19 ` Reinette Chatre
2022-02-23 15:46 ` Jarkko Sakkinen
2022-03-07 16:16 ` Jarkko Sakkinen
2022-02-08 0:45 ` [PATCH V2 20/32] x86/sgx: Tighten accessible memory range after enclave initialization Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 21/32] selftests/sgx: Test two different SGX2 EAUG flows Reinette Chatre
2022-03-07 16:39 ` Jarkko Sakkinen
2022-02-08 0:45 ` [PATCH V2 22/32] x86/sgx: Support modifying SGX page type Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 23/32] x86/sgx: Support complete page removal Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 24/32] Documentation/x86: Introduce enclave runtime management section Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 25/32] selftests/sgx: Introduce dynamic entry point Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 26/32] selftests/sgx: Introduce TCS initialization enclave operation Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 27/32] selftests/sgx: Test complete changing of page type flow Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 28/32] selftests/sgx: Test faulty enclave behavior Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 29/32] selftests/sgx: Test invalid access to removed enclave page Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 30/32] selftests/sgx: Test reclaiming of untouched page Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 31/32] x86/sgx: Free up EPC pages directly to support large page ranges Reinette Chatre
2022-02-08 0:45 ` [PATCH V2 32/32] selftests/sgx: Page removal stress test Reinette Chatre
2022-02-22 20:27 ` [PATCH V2 00/32] x86/sgx and selftests/sgx: Support SGX2 Nathaniel McCallum
2022-02-22 22:39 ` Reinette Chatre
2022-02-23 13:24 ` Nathaniel McCallum
2022-02-23 18:25 ` Reinette Chatre
2022-03-02 16:57 ` Nathaniel McCallum
2022-03-02 21:20 ` Reinette Chatre
2022-03-03 1:13 ` Nathaniel McCallum
2022-03-03 17:49 ` Reinette Chatre
2022-03-04 0:57 ` Jarkko Sakkinen
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