[PATCH v37 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES

Jarkko Sakkinen
2020-09-11T17:40:40Z

Add an ioctl, which performs ENCLS[EADD] that adds new visible page to an
enclave, and optionally ENCLS[EEXTEND] operations that hash the page to the
enclave measurement. By visible we mean a page that can be mapped to the
address range of an enclave.

Acked-by: Jethro Beekman <jethro@fortanix.com>
Tested-by: Jethro Beekman <jethro@fortanix.com>
Tested-by: Haitao Huang <haitao.huang@linux.intel.com>
Tested-by: Chunyang Hui <sanqian.hcy@antfin.com>
Tested-by: Jordan Hand <jorhand@linux.microsoft.com>
Tested-by: Nathaniel McCallum <npmccallum@redhat.com>
Tested-by: Seth Moore <sethmo@google.com>
Tested-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Co-developed-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
arch/x86/include/uapi/asm/sgx.h | 28 ++++
arch/x86/kernel/cpu/sgx/ioctl.c | 289 ++++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/sgx/sgx.h | 1 +
3 files changed, 318 insertions(+)

diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
index c75b375f3770..c42a2ad3ca0b 100644
--- a/arch/x86/include/uapi/asm/sgx.h
+++ b/arch/x86/include/uapi/asm/sgx.h
@@ -8,10 +8,21 @@
#include <linux/types.h>
#include <linux/ioctl.h>

+/**
+ * enum sgx_epage_flags - page control flags
+ * %SGX_PAGE_MEASURE: Measure the page contents with a sequence of
+ * ENCLS[EEXTEND] operations.
+ */
+enum sgx_page_flags {
+ SGX_PAGE_MEASURE = 0x01,
+};
+
#define SGX_MAGIC 0xA4

#define SGX_IOC_ENCLAVE_CREATE \
_IOW(SGX_MAGIC, 0x00, struct sgx_enclave_create)
+#define SGX_IOC_ENCLAVE_ADD_PAGES \
+ _IOWR(SGX_MAGIC, 0x01, struct sgx_enclave_add_pages)

/**
* struct sgx_enclave_create - parameter structure for the
@@ -22,4 +33,21 @@ struct sgx_enclave_create {
__u64 src;
};

+/**
+ * struct sgx_enclave_add_pages - parameter structure for the
+ * %SGX_IOC_ENCLAVE_ADD_PAGE ioctl
+ * @src: start address for the page data
+ * @offset: starting page offset
+ * @length: length of the data (multiple of the page size)
+ * @secinfo: address for the SECINFO data
+ * @flags: page control flags
+ */
+struct sgx_enclave_add_pages {
+ __u64 src;
+ __u64 offset;
+ __u64 length;
+ __u64 secinfo;
+ __u64 flags;
+};
+
#endif /* _UAPI_ASM_X86_SGX_H */
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 352a3c461812..5dcced1df259 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -191,6 +191,292 @@ static long sgx_ioc_enclave_create(struct sgx_encl *encl, void __user *arg)
return ret;
}

+static struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
+ unsigned long offset,
+ u64 secinfo_flags)
+{
+ struct sgx_encl_page *encl_page;
+ unsigned long prot;
+
+ encl_page = kzalloc(sizeof(*encl_page), GFP_KERNEL);
+ if (!encl_page)
+ return ERR_PTR(-ENOMEM);
+
+ encl_page->desc = encl->base + offset;
+ encl_page->encl = encl;
+
+ prot = _calc_vm_trans(secinfo_flags, SGX_SECINFO_R, PROT_READ) |
+ _calc_vm_trans(secinfo_flags, SGX_SECINFO_W, PROT_WRITE) |
+ _calc_vm_trans(secinfo_flags, SGX_SECINFO_X, PROT_EXEC);
+
+ /*
+ * TCS pages must always RW set for CPU access while the SECINFO
+ * permissions are *always* zero - the CPU ignores the user provided
+ * values and silently overwrites them with zero permissions.
+ */
+ if ((secinfo_flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS)
+ prot |= PROT_READ | PROT_WRITE;
+
+ /* Calculate maximum of the VM flags for the page. */
+ encl_page->vm_max_prot_bits = calc_vm_prot_bits(prot, 0);
+
+ return encl_page;
+}
+
+static int sgx_validate_secinfo(struct sgx_secinfo *secinfo)
+{
+ u64 perm = secinfo->flags & SGX_SECINFO_PERMISSION_MASK;
+ u64 pt = secinfo->flags & SGX_SECINFO_PAGE_TYPE_MASK;
+
+ if (pt != SGX_SECINFO_REG && pt != SGX_SECINFO_TCS)
+ return -EINVAL;
+
+ if ((perm & SGX_SECINFO_W) && !(perm & SGX_SECINFO_R))
+ return -EINVAL;
+
+ /*
+ * CPU will silently overwrite the permissions as zero, which means
+ * that we need to validate it ourselves.
+ */
+ if (pt == SGX_SECINFO_TCS && perm)
+ return -EINVAL;
+
+ if (secinfo->flags & SGX_SECINFO_RESERVED_MASK)
+ return -EINVAL;
+
+ if (memchr_inv(secinfo->reserved, 0, sizeof(secinfo->reserved)))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int __sgx_encl_add_page(struct sgx_encl *encl,
+ struct sgx_encl_page *encl_page,
+ struct sgx_epc_page *epc_page,
+ struct sgx_secinfo *secinfo, unsigned long src)
+{
+ struct sgx_pageinfo pginfo;
+ struct vm_area_struct *vma;
+ struct page *src_page;
+ int ret;
+
+ /* Query vma's VM_MAYEXEC as an indirect path_noexec() check. */
+ if (encl_page->vm_max_prot_bits & VM_EXEC) {
+ vma = find_vma(current->mm, src);
+ if (!vma)
+ return -EFAULT;
+
+ if (!(vma->vm_flags & VM_MAYEXEC))
+ return -EACCES;
+ }
+
+ ret = get_user_pages(src, 1, 0, &src_page, NULL);
+ if (ret < 1)
+ return ret;
+
+ pginfo.secs = (unsigned long)sgx_get_epc_addr(encl->secs.epc_page);
+ pginfo.addr = SGX_ENCL_PAGE_ADDR(encl_page);
+ pginfo.metadata = (unsigned long)secinfo;
+ pginfo.contents = (unsigned long)kmap_atomic(src_page);
+
+ ret = __eadd(&pginfo, sgx_get_epc_addr(epc_page));
+
+ kunmap_atomic((void *)pginfo.contents);
+ put_page(src_page);
+
+ return ret ? -EIO : 0;
+}
+
+/*
+ * If the caller requires measurement of the page as a proof for the content,
+ * use EEXTEND to add a measurement for 256 bytes of the page. Repeat this
+ * operation until the entire page is measured."
+ */
+static int __sgx_encl_extend(struct sgx_encl *encl,
+ struct sgx_epc_page *epc_page)
+{
+ int ret;
+ int i;
+
+ for (i = 0; i < 16; i++) {
+ ret = __eextend(sgx_get_epc_addr(encl->secs.epc_page),
+ sgx_get_epc_addr(epc_page) + (i * 0x100));
+ if (ret) {
+ if (encls_failed(ret))
+ ENCLS_WARN(ret, "EEXTEND");
+ return -EIO;
+ }
+ }
+
+ return 0;
+}
+
+static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long src,
+ unsigned long offset, unsigned long length,
+ struct sgx_secinfo *secinfo, unsigned long flags)
+{
+ struct sgx_encl_page *encl_page;
+ struct sgx_epc_page *epc_page;
+ int ret;
+
+ encl_page = sgx_encl_page_alloc(encl, offset, secinfo->flags);
+ if (IS_ERR(encl_page))
+ return PTR_ERR(encl_page);
+
+ epc_page = __sgx_alloc_epc_page();
+ if (IS_ERR(epc_page)) {
+ kfree(encl_page);
+ return PTR_ERR(epc_page);
+ }
+
+ mmap_read_lock(current->mm);
+ mutex_lock(&encl->lock);
+
+ /*
+ * Insert prior to EADD in case of OOM. EADD modifies MRENCLAVE, i.e.
+ * can't be gracefully unwound, while failure on EADD/EXTEND is limited
+ * to userspace errors (or kernel/hardware bugs).
+ */
+ ret = xa_insert(&encl->page_array, PFN_DOWN(encl_page->desc),
+ encl_page, GFP_KERNEL);
+ if (ret)
+ goto err_out_unlock;
+
+ ret = __sgx_encl_add_page(encl, encl_page, epc_page, secinfo,
+ src);
+ if (ret)
+ goto err_out;
+
+ /*
+ * Complete the "add" before doing the "extend" so that the "add"
+ * isn't in a half-baked state in the extremely unlikely scenario
+ * the enclave will be destroyed in response to EEXTEND failure.
+ */
+ encl_page->encl = encl;
+ encl_page->epc_page = epc_page;
+ encl->secs_child_cnt++;
+
+ if (flags & SGX_PAGE_MEASURE) {
+ ret = __sgx_encl_extend(encl, epc_page);
+ if (ret)
+ goto err_out;
+ }
+
+ mutex_unlock(&encl->lock);
+ mmap_read_unlock(current->mm);
+ return ret;
+
+err_out:
+ xa_erase(&encl->page_array, PFN_DOWN(encl_page->desc));
+
+err_out_unlock:
+ mutex_unlock(&encl->lock);
+ mmap_read_unlock(current->mm);
+
+ sgx_free_epc_page(epc_page);
+ kfree(encl_page);
+
+ /*
+ * Destroy enclave on ENCLS failure as this means that EPC has been
+ * invalidated.
+ */
+ if (ret == -EIO) {
+ mutex_lock(&encl->lock);
+ sgx_encl_destroy(encl);
+ mutex_unlock(&encl->lock);
+ }
+
+ return ret;
+}
+
+/**
+ * sgx_ioc_enclave_add_pages() - The handler for %SGX_IOC_ENCLAVE_ADD_PAGES
+ * @encl: an enclave pointer
+ * @arg: a user pointer to a struct sgx_enclave_add_pages instance
+ *
+ * Add one or more pages to an uninitialized enclave, and optionally extend the
+ * measurement with the contents of the page. The SECINFO and measurement mask
+ * are applied to all pages.
+ *
+ * A SECINFO for a TCS is required to always contain zero permissions because
+ * CPU silently zeros them. Allowing anything else would cause a mismatch in
+ * the measurement.
+ *
+ * mmap()'s protection bits are capped by the page permissions. For each page
+ * address, the maximum protection bits are computed with the following
+ * heuristics:
+ *
+ * 1. A regular page: PROT_R, PROT_W and PROT_X match the SECINFO permissions.
+ * 2. A TCS page: PROT_R | PROT_W.
+ *
+ * mmap() is not allowed to surpass the minimum of the maximum protection bits
+ * within the given address range.
+ *
+ * If ENCLS opcode fails, that effectively means that EPC has been invalidated.
+ * When this happens the enclave is destroyed and -EIO is returned to the
+ * caller.
+ *
+ * Return:
+ * length of the data processed on success,
+ * -EACCES if an executable source page is located in a noexec partition,
+ * -EIO if either ENCLS[EADD] or ENCLS[EEXTEND] fails
+ * -errno otherwise
+ */
+static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg)
+{
+ struct sgx_enclave_add_pages addp;
+ struct sgx_secinfo secinfo;
+ unsigned long c;
+ int ret;
+
+ if ((atomic_read(&encl->flags) & SGX_ENCL_INITIALIZED) ||
+ !(atomic_read(&encl->flags) & SGX_ENCL_CREATED))
+ return -EINVAL;
+
+ if (copy_from_user(&addp, arg, sizeof(addp)))
+ return -EFAULT;
+
+ if (!IS_ALIGNED(addp.offset, PAGE_SIZE) ||
+ !IS_ALIGNED(addp.src, PAGE_SIZE))
+ return -EINVAL;
+
+ if (!(access_ok(addp.src, PAGE_SIZE)))
+ return -EFAULT;
+
+ if (addp.length & (PAGE_SIZE - 1))
+ return -EINVAL;
+
+ if (addp.offset + addp.length - PAGE_SIZE >= encl->size)
+ return -EINVAL;
+
+ if (copy_from_user(&secinfo, (void __user *)addp.secinfo,
+ sizeof(secinfo)))
+ return -EFAULT;
+
+ if (sgx_validate_secinfo(&secinfo))
+ return -EINVAL;
+
+ for (c = 0 ; c < addp.length; c += PAGE_SIZE) {
+ if (c == SGX_MAX_ADD_PAGES_LENGTH || signal_pending(current)) {
+ ret = c;
+ break;
+ }
+
+ if (need_resched())
+ cond_resched();
+
+ ret = sgx_encl_add_page(encl, addp.src + c, addp.offset + c,
+ addp.length - c, &secinfo, addp.flags);
+ if (ret)
+ break;
+ }
+
+ if (copy_to_user(arg, &addp, sizeof(addp)))
+ return -EFAULT;
+
+ return c;
+}
+
long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
{
struct sgx_encl *encl = filep->private_data;
@@ -209,6 +495,9 @@ long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
case SGX_IOC_ENCLAVE_CREATE:
ret = sgx_ioc_enclave_create(encl, (void __user *)arg);
break;
+ case SGX_IOC_ENCLAVE_ADD_PAGES:
+ ret = sgx_ioc_enclave_add_pages(encl, (void __user *)arg);
+ break;
default:
ret = -ENOIOCTLCMD;
break;
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index fce756c3434b..8d126070db1e 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -34,6 +34,7 @@ struct sgx_epc_section {

#define SGX_EPC_SECTION_MASK GENMASK(7, 0)
#define SGX_MAX_EPC_SECTIONS (SGX_EPC_SECTION_MASK + 1)
+#define SGX_MAX_ADD_PAGES_LENGTH 0x100000

extern struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];

--
2.25.1