[PATCH for_v23 3/4] x86/sgx: Fix EEXTEND error handling

[Sean Christopherson <sean.j.christopherson@intel.com>]

Rework EEXTEND error handling to fix issues related to destroying the
enclave in response to EEXTEND failure.  At the time of EEXTEND, the
page is already visibile in the sense that it has been added to the
radix tree, and therefore will be processed by sgx_encl_destroy().  This
means the "add" part needs to be fully completed prior to invoking
sgx_encl_destroy() in order to avoid consuming half-baked state.

Move sgx_encl_destroy() to the call site of __sgx_encl_extend() so that
it is somewhat more obvious why the add needs to complete before doing
EEXTEND.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kernel/cpu/sgx/ioctl.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 61a2a7b6677e..fd4117f18564 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -351,18 +351,14 @@ static int __sgx_encl_extend(struct sgx_encl *encl,
 	for_each_set_bit(i, &mrmask, 16) {
 		ret = __eextend(sgx_epc_addr(encl->secs.epc_page),
 				sgx_epc_addr(epc_page) + (i * 0x100));
-		if (ret)
-			goto err_out;
+		if (ret) {
+			if (encls_failed(ret))
+				ENCLS_WARN(ret, "EEXTEND");
+			return -EFAULT;
+		}
 	}
 
 	return 0;
-
-err_out:
-	if (encls_failed(ret))
-		ENCLS_WARN(ret, "EEXTEND");
-
-	sgx_encl_destroy(encl);
-	return -EFAULT;
 }
 
 static int sgx_encl_add_page(struct sgx_encl *encl,
@@ -415,19 +411,24 @@ static int sgx_encl_add_page(struct sgx_encl *encl,
 	if (ret)
 		goto err_out;
 
-	ret = __sgx_encl_extend(encl, epc_page, addp->mrmask);
-	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
+	 * the enclave will be destroyed in response to EEXTEND failure.
+	 */
 	encl_page->encl = encl;
 	encl_page->epc_page = epc_page;
 	encl->secs_child_cnt++;
 
-	sgx_mark_page_reclaimable(encl_page->epc_page);
+	ret = __sgx_encl_extend(encl, epc_page, addp->mrmask);
+	if (ret)
+		sgx_encl_destroy(encl);
+	else
+		sgx_mark_page_reclaimable(encl_page->epc_page);
 
 	mutex_unlock(&encl->lock);
 	up_read(&current->mm->mmap_sem);
-	return 0;
+	return ret;
 
 err_out:
 	radix_tree_delete(&encl_page->encl->page_tree,
-- 
2.22.0