[RFC PATCH v2.1 12/30] x86/sgx: Create utility to validate user provided offset and length

From: Jarkko Sakkinen <jarkko@kernel.org>
To: linux-sgx@vger.kernel.org
Cc: Nathaniel McCallum <nathaniel@profian.com>,
	Reinette Chatre <reinette.chatre@intel.com>,
	Jarkko Sakkinen <jarkko@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org (open list:X86 ARCHITECTURE (32-BIT
	AND 64-BIT))
Subject: [RFC PATCH v2.1 12/30] x86/sgx: Create utility to validate user provided offset and length
Date: Fri,  4 Mar 2022 11:35:06 +0200	[thread overview]
Message-ID: <20220304093524.397485-12-jarkko@kernel.org> (raw)
In-Reply-To: <20220304093524.397485-1-jarkko@kernel.org>

From: Reinette Chatre <reinette.chatre@intel.com>

User provided offset and length is validated when parsing the parameters
of the SGX_IOC_ENCLAVE_ADD_PAGES ioctl(). Extract this validation
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>
---
 arch/x86/kernel/cpu/sgx/ioctl.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index 83df20e3e633..f487549bccba 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -372,6 +372,26 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long src,
 	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 || length & (PAGE_SIZE - 1))
+		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,
-- 
2.35.1

