[PATCH] x86/sgx: Add overflow check in sgx_validate_offset_length()

From: Borys <borysp@invisiblethingslab.com>
To: 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, "H. Peter Anvin" <hpa@zytor.com>,
	linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: "Reinette Chatre" <reinette.chatre@intel.com>,
	"Michał Kowalczyk" <mkow@invisiblethingslab.com>
Subject: [PATCH] x86/sgx: Add overflow check in sgx_validate_offset_length()
Date: Wed, 5 Oct 2022 00:59:03 +0200	[thread overview]
Message-ID: <0d91ac79-6d84-abed-5821-4dbe59fa1a38@invisiblethingslab.com> (raw)

sgx_validate_offset_length() function verifies "offset" and "length"
arguments provided by userspace, but was missing an overflow check on
their addition.
This code was originally introduced in commit c6d26d370767 ("x86/sgx:
Add SGX_IOC_ENCLAVE_ADD_PAGES") and later refactored in commit
dda03e2c331b ("x86/sgx: Create utility to validate user provided offset
and length").

Fixes: c6d26d370767 ("x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES")
Signed-off-by: Borys Popławski <borysp@invisiblethingslab.com>
---
 Applies on top of tip/x86/sgx ee56a283988d739c25d2d00ffb22707cb487ab47

 arch/x86/kernel/cpu/sgx/ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index ebe79d60619f..da8b8ea6b063 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -356,6 +356,9 @@ static int sgx_validate_offset_length(struct sgx_encl *encl,
 	if (!length || !IS_ALIGNED(length, PAGE_SIZE))
 		return -EINVAL;
 
+	if (offset + length < offset)
+		return -EINVAL;
+
 	if (offset + length - PAGE_SIZE >= encl->size)
 		return -EINVAL;
 
-- 
2.37.3

