Commit 633b0616 authored by Ira Weiny's avatar Ira Weiny Committed by Borislav Petkov
Browse files

x86/sgx: Remove unnecessary kmap() from sgx_ioc_enclave_init() 



kmap() is inefficient and is being replaced by kmap_local_page(), if
possible. There is no readily apparent reason why initp_page needs to be
allocated and kmap'ed() except that 'sigstruct' needs to be page-aligned
and 'token' 512 byte-aligned.

Rather than change it to kmap_local_page(), use kmalloc() instead
because kmalloc() can give this alignment when allocating PAGE_SIZE
bytes.

Remove the alloc_page()/kmap() and replace with kmalloc(PAGE_SIZE, ...)
to get a page aligned kernel address.

In addition, add a comment to document the alignment requirements so that
others don't attempt to 'fix' this again.

 [ bp: Massage commit message. ]

Signed-off-by: default avatarIra Weiny <ira.weiny@intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210324182246.2484875-1-ira.weiny@intel.com
parent f33dece7

arch/x86/kernel/cpu/sgx/ioctl.c

+8 −6
Original line number Diff line number Diff line
@@ -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;
@@ -615,11 +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' must be on a page boundary and 'token' on a 512 byte

	 * boundary.  kmalloc() will give this alignment when allocating

	 * PAGE_SIZE bytes.

	 */

	sigstruct = kmalloc(PAGE_SIZE, 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);
@@ -645,8 +648,7 @@ 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(sigstruct);

	return ret;

}