From: Kees Cook <keescook@chromium.org>
To: linux-hardening@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
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,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 22/82] x86/sgx: Refactor intentional wrap-around calculation
Date: Mon, 22 Jan 2024 16:26:57 -0800 [thread overview]
Message-ID: <20240123002814.1396804-22-keescook@chromium.org> (raw)
In-Reply-To: <20240122235208.work.748-kees@kernel.org>
In an effort to separate intentional arithmetic wrap-around from
unexpected wrap-around, we need to refactor places that depend on this
kind of math. One of the most common code patterns of this is:
VAR + value < VAR
Notably, this is considered "undefined behavior" for signed and pointer
types, which the kernel works around by using the -fno-strict-overflow
option in the build[1] (which used to just be -fwrapv). Regardless, we
want to get the kernel source to the position where we can meaningfully
instrument arithmetic wrap-around conditions and catch them when they
are unexpected, regardless of whether they are signed[2], unsigned[3],
or pointer[4] types.
Refactor open-coded unsigned wrap-around addition test to use
check_add_overflow(), retaining the result for later usage (which removes
the redundant open-coded addition). This paves the way to enabling the
wrap-around sanitizers in the future.
Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
Link: https://github.com/KSPP/linux/issues/26 [2]
Link: https://github.com/KSPP/linux/issues/27 [3]
Link: https://github.com/KSPP/linux/issues/344 [4]
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-sgx@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/kernel/cpu/sgx/ioctl.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index b65ab214bdf5..4b8f6c9f8ef5 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -350,16 +350,18 @@ static int sgx_validate_offset_length(struct sgx_encl *encl,
unsigned long offset,
unsigned long length)
{
+ unsigned long sum;
+
if (!IS_ALIGNED(offset, PAGE_SIZE))
return -EINVAL;
if (!length || !IS_ALIGNED(length, PAGE_SIZE))
return -EINVAL;
- if (offset + length < offset)
+ if (check_add_overflow(offset, length, &sum))
return -EINVAL;
- if (offset + length - PAGE_SIZE >= encl->size)
+ if (sum - PAGE_SIZE >= encl->size)
return -EINVAL;
return 0;
--
2.34.1
next parent reply other threads:[~2024-01-23 0:29 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240122235208.work.748-kees@kernel.org>
2024-01-23 0:26 ` Kees Cook [this message]
2024-01-23 9:15 ` [PATCH 22/82] x86/sgx: Refactor intentional wrap-around calculation Jarkko Sakkinen
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