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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: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210324182246.2484875-1-ira.weiny@intel.com
This commit is contained in:
Ira Weiny 2021-03-24 11:22:46 -07:00 committed by Borislav Petkov
parent f33dece70e
commit 633b0616cf
1 changed files with 8 additions and 6 deletions
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14
arch/x86/kernel/cpu/sgx/ioctl.c
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@ -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;
}