x86/sgx: Create utility to validate user provided offset and length

User provided offset and length is validated when parsing the parameters
of the SGX_IOC_ENCLAVE_ADD_PAGES ioctl(). Extract this validation
(with consistent use of IS_ALIGNED) into a utility that can be used
by the SGX2 ioctl()s that will also provide these values.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/767147bc100047abed47fe27c592901adfbb93a2.1652137848.git.reinette.chatre@intel.com

diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 83df20e3e633353ca0b707cda6cae51cb6f09714..a66795e0b685a22d8e452c8045be70dffde60b00 100644 (file)
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -372,6 +372,26 @@ err_out_free:
        return ret;
 }
 
+/*
+ * Ensure user provided offset and length values are valid for
+ * an enclave.
+ */
+static int sgx_validate_offset_length(struct sgx_encl *encl,
+                                     unsigned long offset,
+                                     unsigned long length)
+{
+       if (!IS_ALIGNED(offset, PAGE_SIZE))
+               return -EINVAL;
+
+       if (!length || !IS_ALIGNED(length, PAGE_SIZE))
+               return -EINVAL;
+
+       if (offset + length - PAGE_SIZE >= encl->size)
+               return -EINVAL;
+
+       return 0;
+}
+
 /**
  * sgx_ioc_enclave_add_pages() - The handler for %SGX_IOC_ENCLAVE_ADD_PAGES
  * @encl:       an enclave pointer
@@ -425,14 +445,10 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg)
        if (copy_from_user(&add_arg, arg, sizeof(add_arg)))
                return -EFAULT;
 
-       if (!IS_ALIGNED(add_arg.offset, PAGE_SIZE) ||
-           !IS_ALIGNED(add_arg.src, PAGE_SIZE))
-               return -EINVAL;
-
-       if (!add_arg.length || add_arg.length & (PAGE_SIZE - 1))
+       if (!IS_ALIGNED(add_arg.src, PAGE_SIZE))
                return -EINVAL;
 
-       if (add_arg.offset + add_arg.length - PAGE_SIZE >= encl->size)
+       if (sgx_validate_offset_length(encl, add_arg.offset, add_arg.length))
                return -EINVAL;
 
        if (copy_from_user(&secinfo, (void __user *)add_arg.secinfo,