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: Martyn Welch <martyn@xxxxxxxxxxxx> Cc: Manohar Vanga <manohar.vanga@xxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Soumya Negi <soumya.negi97@xxxxxxxxx> Cc: Alexon Oliveira <alexondunkan@xxxxxxxxx> Cc: linux-staging@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- drivers/staging/vme_user/vme.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/vme_user/vme.c b/drivers/staging/vme_user/vme.c index e9461a7a7ab8..a0acf2a295cd 100644 --- a/drivers/staging/vme_user/vme.c +++ b/drivers/staging/vme_user/vme.c @@ -165,7 +165,7 @@ int vme_check_window(struct vme_bridge *bridge, u32 aspace, { int retval = 0; - if (vme_base + size < size) + if (add_would_overflow(size, vme_base)) return -EINVAL; switch (aspace) { -- 2.34.1
