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: Sean Christopherson <seanjc@google.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Nataliia Bondarevska <bondarn@google.com>

diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c
index 7f8d1e11dbee24be7482fcd19f6eb51c75e5e49e..79d6020dfe9c89118d3088f23a9ea619a0231dab 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/driver.c
+++ b/arch/x86/kernel/cpu/sgx/driver.c
@@ -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;

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 308dbbae6c6e52014ba7c3290203d9cd7fe82aa7..cf149b9f4916b08d74fca87d155d6aa81f2feda1 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -765,6 +765,7 @@ void sgx_encl_release(struct kref *ref)
        WARN_ON_ONCE(encl->secs.epc_page);
 
        kfree(encl);
+       sgx_dec_usage_count();
 }
 
 /*

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 2de01b379aa322aef33e4b1039e5469efb8bf927..3a5cbd1c170ec0c06f79caa46f9869983b662254 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -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;

diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index d2dad21259a8d2d4cf06d4d908690625501fdab3..f5940393d9bd53afd268c7c536cca14da486edfb 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -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 */

diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c
index 7aaa3652e31d15022a9d956944cd14c099ea0740..b649c0610019a9178cfab675da69aea6fbce67af 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/virt.c
+++ b/arch/x86/kernel/cpu/sgx/virt.c
@@ -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)
 {