Add a memory barrier pair to ensure all enclave state is visible in
memory prior to SGX_ENCL_CREATED being set. Without the barries, adding
pages and/or initializing the enclaves could theoretically consume stale
data.
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kernel/cpu/sgx/ioctl.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 911ff3b0f061..7134d68aecb3 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -163,6 +163,15 @@ static struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
return encl_page;
}
+static bool is_encl_created(struct sgx_encl *encl)
+{
+ bool created = encl->flags & SGX_ENCL_CREATED;
+
+ /* Pairs with smp_wmb() in sgx_encl_create(). */
+ smp_rmb();
+ return created;
+}
+
static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
{
unsigned long encl_size = secs->size + PAGE_SIZE;
@@ -231,8 +240,9 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
/*
* Set SGX_ENCL_CREATED only after the enclave is fully prepped. This
* allows other flows to check if the enclave has been created without
- * taking encl->lock.
+ * taking encl->lock. Pairs with smp_rmb() in is_encl_created().
*/
+ smp_wmb();
encl->flags |= SGX_ENCL_CREATED;
mutex_unlock(&encl->lock);
@@ -478,7 +488,7 @@ static long sgx_ioc_enclave_add_page(struct file *filep, void __user *arg)
struct sgx_enclave_add_page addp;
struct sgx_secinfo secinfo;
- if (!(encl->flags & SGX_ENCL_CREATED))
+ if (!is_encl_created(encl))
return -EINVAL;
if (copy_from_user(&addp, arg, sizeof(addp)))
@@ -611,7 +621,7 @@ static long sgx_ioc_enclave_init(struct file *filep, void __user *arg)
struct page *initp_page;
int ret;
- if (!(encl->flags & SGX_ENCL_CREATED))
+ if (!is_encl_created(encl))
return -EINVAL;
if (copy_from_user(&einit, arg, sizeof(einit)))
--
2.22.0
