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: Karol Herbst <kherbst@xxxxxxxxxx> Cc: Lyude Paul <lyude@xxxxxxxxxx> Cc: Danilo Krummrich <dakr@xxxxxxxxxx> Cc: David Airlie <airlied@xxxxxxxxx> Cc: Daniel Vetter <daniel@xxxxxxxx> Cc: Ben Skeggs <bskeggs@xxxxxxxxxx> Cc: Dave Airlie <airlied@xxxxxxxxxx> Cc: Julia Lawall <Julia.Lawall@xxxxxxxx> Cc: Jiang Jian <jiangjian@xxxxxxxxxx> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Cc: nouveau@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c index 9c97800fe037..6ca1a82ccbc1 100644 --- a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c @@ -1149,13 +1149,15 @@ nvkm_vmm_ctor(const struct nvkm_vmm_func *func, struct nvkm_mmu *mmu, vmm->root = RB_ROOT; if (managed) { + u64 sum; + /* Address-space will be managed by the client for the most * part, except for a specified area where NVKM allocations * are allowed to be placed. */ vmm->start = 0; vmm->limit = 1ULL << bits; - if (addr + size < addr || addr + size > vmm->limit) + if (check_add_overflow(addr, size, &sum) || sum > vmm->limit) return -EINVAL; /* Client-managed area before the NVKM-managed area. */ @@ -1174,7 +1176,7 @@ nvkm_vmm_ctor(const struct nvkm_vmm_func *func, struct nvkm_mmu *mmu, } /* Client-managed area after the NVKM-managed area. */ - addr = addr + size; + addr = sum; size = vmm->limit - addr; if (size && (ret = nvkm_vmm_ctor_managed(vmm, addr, size))) return ret; -- 2.34.1
