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From:   ira.weiny@intel.com
To:     Jarkko Sakkinen <jarkko@kernel.org>
Cc:     Ira Weiny <ira.weiny@intel.com>, linux-kernel@vger.kernel.org,
        linux-sgx@vger.kernel.org
Subject: [PATCH] x86: Remove unnecessary kmap() from sgx_ioc_enclave_init()
Date:   Thu, 28 Jan 2021 16:14:59 -0800
Message-Id: <20210129001459.1538805-1-ira.weiny@intel.com>
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From: Ira Weiny <ira.weiny@intel.com>

There is no reason to alloc a page and kmap it to store this temporary
data from the user.  This is especially true when we are trying to
remove kmap usages.  Also placing the token pointer 1/2 way into the
page is fragile.

Replace this allocation with two kzalloc()'s which also removes the need
for the memset().

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 arch/x86/kernel/cpu/sgx/ioctl.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 90a5caf76939..9c9019760585 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -604,7 +604,6 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
 {
 	struct sgx_sigstruct *sigstruct;
 	struct sgx_enclave_init init_arg;
-	struct page *initp_page;
 	void *token;
 	int ret;
 
@@ -615,13 +614,15 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
 	if (copy_from_user(&init_arg, arg, sizeof(init_arg)))
 		return -EFAULT;
 
-	initp_page = alloc_page(GFP_KERNEL);
-	if (!initp_page)
+	sigstruct = kzalloc(sizeof(*sigstruct), GFP_KERNEL);
+	if (!sigstruct)
 		return -ENOMEM;
 
-	sigstruct = kmap(initp_page);
-	token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2);
-	memset(token, 0, SGX_LAUNCH_TOKEN_SIZE);
+	token = kzalloc(SGX_LAUNCH_TOKEN_SIZE, GFP_KERNEL);
+	if (!token) {
+		ret = -ENOMEM;
+		goto free_sigstruct;
+	}
 
 	if (copy_from_user(sigstruct, (void __user *)init_arg.sigstruct,
 			   sizeof(*sigstruct))) {
@@ -645,8 +646,9 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
 	ret = sgx_encl_init(encl, sigstruct, token);
 
 out:
-	kunmap(initp_page);
-	__free_page(initp_page);
+	kfree(token);
+free_sigstruct:
+	kfree(sigstruct);
 	return ret;
 }
 
-- 
2.28.0.rc0.12.gb6a658bd00c9