[PATCH] x86/sgx: Refine rollback in SGX_IOC_ENCLAVE_ADD_PAGE

[Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>]

Revert back 'count' to struct sgx_enclave_add_pages as in most of the
cases enclave can be recovered. Refine the documentation to better
describe the enclave is persisted.

Move the check for -EIO from sgx_encl_add_page() to
sgx_ioc_enclave_pages() to make it more visible. It was quite
hidden over there.

Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
 arch/x86/include/uapi/asm/sgx.h | 12 +++++++-----
 arch/x86/kernel/cpu/sgx/ioctl.c | 29 ++++++++++++++---------------
 2 files changed, 21 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
index 1564d7f88597..ec5157b2ff50 100644
--- a/arch/x86/include/uapi/asm/sgx.h
+++ b/arch/x86/include/uapi/asm/sgx.h
@@ -45,13 +45,15 @@ struct sgx_enclave_create  {
  * @length:	length of the data (multiple of the page size)
  * @secinfo:	address for the SECINFO data
  * @flags:	page control flags
+ * @count:	number of bytes added (multiple of the page size)
  */
 struct sgx_enclave_add_pages {
-	__u64	src;
-	__u64	offset;
-	__u64	length;
-	__u64	secinfo;
-	__u64	flags;
+	__u64 src;
+	__u64 offset;
+	__u64 length;
+	__u64 secinfo;
+	__u64 flags;
+	__u64 count;
 };
 
 /**
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 30de66f4247b..d10179b47daa 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -449,16 +449,6 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long src,
 	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;
 }
 
@@ -487,12 +477,15 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long src,
  *
  * 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.
+ * caller. In this situation the function destroys the enclave as it cannot
+ * be recovered.
  *
  * 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
+ *   -ENOMEM if the system is out of EPC pages,
+ *   -EINTR if the call was interrupted before any data was processed,
+ *   -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)
@@ -549,10 +542,16 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg)
 			break;
 	}
 
-	if (ret)
-		return ret;
+	addp.count = c;
+
+	/* On EADD or EEXTEND failure, destroy the enclave. */
+	if (ret == -EIO) {
+		mutex_lock(&encl->lock);
+		sgx_encl_destroy(encl);
+		mutex_unlock(&encl->lock);
+	}
 
-	return c;
+	return ret;
 }
 
 static int __sgx_get_key_hash(struct crypto_shash *tfm, const void *modulus,
-- 
2.25.1