Commit 483fc19e authored by Elena Reshetova's avatar Elena Reshetova Committed by Dave Hansen
Browse files

x86/sgx: Introduce functions to count the sgx_(vepc_)open() 



Currently, when SGX is compromised and the microcode update fix is applied,
the machine needs to be rebooted to invalidate old SGX crypto-assets and
make SGX be in an updated safe state. It's not friendly for the cloud.

To avoid having to reboot, a new ENCLS[EUPDATESVN] is introduced to update
SGX environment at runtime. This process needs to be done when there's no
SGX users to make sure no compromised enclaves can survive from the update
and allow the system to regenerate crypto-assets.

For now there's no counter to track the active SGX users of host enclave
and virtual EPC. Introduce such counter mechanism so that the EUPDATESVN
can be done only when there's no SGX users.

Define placeholder functions sgx_inc/dec_usage_count() that are used to
increment and decrement such a counter. Also, wire the call sites for
these functions. Encapsulate the current sgx_(vepc_)open() to
__sgx_(vepc_)open() to make the new sgx_(vepc_)open() easy to read.

The definition of the counter itself and the actual implementation of
sgx_inc/dec_usage_count() functions come next.

Note: The EUPDATESVN, which may fail, will be done in
sgx_inc_usage_count(). Make it return 'int' to make subsequent patches
which implement EUPDATESVN easier to review. For now it always returns
success.

Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarKai Huang <kai.huang@intel.com>
Reviewed-by: default avatarJarkko Sakkinen <jarkko@kernel.org>
Tested-by: default avatarNataliia Bondarevska <bondarn@google.com>
parent 3a866087

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

+18 −1
Original line number Diff line number Diff line
@@ -14,7 +14,7 @@ u64 sgx_attributes_reserved_mask; 
u64 sgx_xfrm_reserved_mask = ~0x3;

u32 sgx_misc_reserved_mask;



static int sgx_open(struct inode *inode, struct file *file)

static int __sgx_open(struct inode *inode, struct file *file)

{

	struct sgx_encl *encl;

	int ret;
@@ -41,6 +41,23 @@ static int sgx_open(struct inode *inode, struct file *file) 
	return 0;

}



static int sgx_open(struct inode *inode, struct file *file)

{

	int ret;



	ret = sgx_inc_usage_count();

	if (ret)

		return ret;



	ret = __sgx_open(inode, file);

	if (ret) {

		sgx_dec_usage_count();

		return ret;

	}



	return 0;

}



static int sgx_release(struct inode *inode, struct file *file)

{

	struct sgx_encl *encl = file->private_data;

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

+1 −0
Original line number Diff line number Diff line
@@ -765,6 +765,7 @@ void sgx_encl_release(struct kref *ref) 
	WARN_ON_ONCE(encl->secs.epc_page);



	kfree(encl);

	sgx_dec_usage_count();

}



/*

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

+10 −0
Original line number Diff line number Diff line
@@ -917,6 +917,16 @@ int sgx_set_attribute(unsigned long *allowed_attributes, 
}

EXPORT_SYMBOL_GPL(sgx_set_attribute);



int sgx_inc_usage_count(void)

{

	return 0;

}



void sgx_dec_usage_count(void)

{

	return;

}



static int __init sgx_init(void)

{

	int ret;

arch/x86/kernel/cpu/sgx/sgx.h

+3 −0
Original line number Diff line number Diff line
@@ -102,6 +102,9 @@ static inline int __init sgx_vepc_init(void) 
}

#endif



int sgx_inc_usage_count(void);

void sgx_dec_usage_count(void);



void sgx_update_lepubkeyhash(u64 *lepubkeyhash);



#endif /* _X86_SGX_H */

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

+19 −1
Original line number Diff line number Diff line
@@ -255,10 +255,11 @@ static int sgx_vepc_release(struct inode *inode, struct file *file) 
	xa_destroy(&vepc->page_array);

	kfree(vepc);



	sgx_dec_usage_count();

	return 0;

}



static int sgx_vepc_open(struct inode *inode, struct file *file)

static int __sgx_vepc_open(struct inode *inode, struct file *file)

{

	struct sgx_vepc *vepc;
@@ -273,6 +274,23 @@ static int sgx_vepc_open(struct inode *inode, struct file *file) 
	return 0;

}



static int sgx_vepc_open(struct inode *inode, struct file *file)

{

	int ret;



	ret = sgx_inc_usage_count();

	if (ret)

		return ret;



	ret =  __sgx_vepc_open(inode, file);

	if (ret) {

		sgx_dec_usage_count();

		return ret;

	}



	return 0;

}



static long sgx_vepc_ioctl(struct file *file,

			   unsigned int cmd, unsigned long arg)

{