From: Kees Cook <keescook@chromium.org>
To: linux-hardening@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
Konstantin Komarov <almaz.alexandrovich@paragon-software.com>,
ntfs3@lists.linux.dev,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 66/82] fs/ntfs3: Refactor intentional wrap-around test
Date: Mon, 22 Jan 2024 16:27:41 -0800 [thread overview]
Message-ID: <20240123002814.1396804-66-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 wrap-around addition test to use add_would_overflow().
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: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: ntfs3@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/ntfs3/record.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/ntfs3/record.c b/fs/ntfs3/record.c
index 53629b1f65e9..8cd738c1dbe6 100644
--- a/fs/ntfs3/record.c
+++ b/fs/ntfs3/record.c
@@ -235,7 +235,7 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
}
/* Overflow check. */
- if (off + asize < off)
+ if (add_would_overflow(off, asize))
return NULL;
prev_type = le32_to_cpu(attr->type);
@@ -266,7 +266,7 @@ struct ATTRIB *mi_enum_attr(struct mft_inode *mi, struct ATTRIB *attr)
return NULL;
/* Check overflow and boundary. */
- if (off + asize < off || off + asize > used)
+ if (add_would_overflow(off, asize) || off + asize > used)
return NULL;
/* Check size of attribute. */
--
2.34.1
parent reply other threads:[~2024-01-23 0:29 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <20240122235208.work.748-kees@kernel.org>]
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