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@xxxxxxxxxxxxxxxxxxxx> Cc: ntfs3@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- 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
