From: Ira Weiny <ira.weiny@xxxxxxxxx> kmap is inefficient and we are trying to reduce the usage in the kernel. There is no readily apparent reason why the initp_page page needs to be allocated and kmap'ed() but sigstruct needs to be page aligned and token 512 byte aligned. In this case page_address() can be used instead of kmap_local_page() as a much more efficient way to use the address because the page is allocated GFP_KERNEL. Remove the kmap and replace with page_address() to get a kernel address for the alloc'ed page. In addition add a comment regarding the alignment requirements as well as 2 BUILD_BUG_ON's to ensure future changes to sigstruct and token do not go unnoticed and cause a bug. Cc: Sean Christopherson <seanjc@xxxxxxxxxx>, Cc: Jethro Beekman <jethro@xxxxxxxxxxxx>, Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> --- Changes from v1[1]: Use page_address() instead of kcmalloc() to ensure sigstruct is page aligned Use BUILD_BUG_ON to ensure token and sigstruct don't collide. [1] https://lore.kernel.org/lkml/20210129001459.1538805-1-ira.weiny@xxxxxxxxx/ --- arch/x86/kernel/cpu/sgx/ioctl.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c index 90a5caf76939..678b02d67c3c 100644 --- a/arch/x86/kernel/cpu/sgx/ioctl.c +++ b/arch/x86/kernel/cpu/sgx/ioctl.c @@ -615,11 +615,18 @@ 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; + /* + * sigstruct must be on a page boundry and token on a 512 byte boundry + * so use alloc_page/page_address instead of a kmalloc(). + */ initp_page = alloc_page(GFP_KERNEL); if (!initp_page) return -ENOMEM; - sigstruct = kmap(initp_page); + sigstruct = page_address(initp_page); + + BUILD_BUG_ON(sizeof(*sigstruct) > (PAGE_SIZE/2)); + BUILD_BUG_ON(SGX_LAUNCH_TOKEN_SIZE > (PAGE_SIZE/2)); token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2); memset(token, 0, SGX_LAUNCH_TOKEN_SIZE); @@ -645,7 +652,6 @@ 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); return ret; } -- 2.28.0.rc0.12.gb6a658bd00c9
