On Fri, May 15, 2020 at 03:44:00AM +0300, Jarkko Sakkinen wrote:

+long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
+{
+	struct sgx_encl *encl = filep->private_data;
+	int ret, encl_flags;
+
+	encl_flags = atomic_fetch_or(SGX_ENCL_IOCTL, &encl->flags);
+	if (encl_flags & SGX_ENCL_IOCTL)
+		return -EBUSY;
+
+	if (encl_flags & SGX_ENCL_DEAD)
+		return -EFAULT;

Returning immediately is wrong as it leaves SGX_ENCL_IOCTL set.  This results
in the application seeing -EBUSY on future ioctls() instead of -EFAULT.  Can be
fixed as below.  Do you want me to send a formal patch on linux-sgx?

diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 77757a74644d..df35a79e915c 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c

@@ -751,8 +751,10 @@ long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
        if (encl_flags & SGX_ENCL_IOCTL)
                return -EBUSY;

-       if (encl_flags & SGX_ENCL_DEAD)
-               return -EFAULT;
+       if (encl_flags & SGX_ENCL_DEAD) {
+               ret = -EFAULT;
+               goto out;
+       }

        switch (cmd) {
        case SGX_IOC_ENCLAVE_CREATE:

@@ -772,6 +774,7 @@ long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
                break;
        }

+out:
        atomic_andnot(SGX_ENCL_IOCTL, &encl->flags);

        return ret;

+
+	switch (cmd) {
+	case SGX_IOC_ENCLAVE_CREATE:
+		ret = sgx_ioc_enclave_create(encl, (void __user *)arg);
+		break;
+	case SGX_IOC_ENCLAVE_ADD_PAGES:
+		ret = sgx_ioc_enclave_add_pages(encl, (void __user *)arg);
+		break;
+	case SGX_IOC_ENCLAVE_INIT:
+		ret = sgx_ioc_enclave_init(encl, (void __user *)arg);
+		break;
+	default:
+		ret = -ENOIOCTLCMD;
+		break;
+	}
+
+	atomic_andnot(SGX_ENCL_IOCTL, &encl->flags);
+
+	return ret;
+}