On Thu, Jun 01, 2023 at 02:38:58PM +0000, Chuck Lever III wrote: > > - if (len > SIZE_MAX / sizeof(*p)) > > + if (unlikely(SIZE_MAX == U32_MAX ? (len > U32_MAX / sizeof(*p)) : 0)) > This is a bug in Clang. Generally the rule, is that if there is a bug in the static checker then you should fix the checker instead of the code. Smatch used to have this same bug but I fixed it. So it's not something which is unfixable. This doesn't cause a problem for normal Clang builds, only for W=1, right? But, here is a nicer way to fix it. You can send this, or I can send it tomorrow with your Reported-by? regards, dan carpenter Fix the following warning observed when building 64-bit (actually arm64) kernel with clang-17 (make LLVM=1 W=1): include/linux/sunrpc/xdr.h:779:10: warning: result of comparison of constant 4611686018427387903 with expression of type '__u32' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare] 779 | if (len > SIZE_MAX / sizeof(*p)) That is, an overflow check makes sense for 32-bit kernel only. Silence the Clang warning and make the code nicer by using the size_mul() function to prevent integer overflows. diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h index f89ec4b5ea16..dbf7620a2853 100644 --- a/include/linux/sunrpc/xdr.h +++ b/include/linux/sunrpc/xdr.h @@ -775,9 +775,7 @@ xdr_stream_decode_uint32_array(struct xdr_stream *xdr, if (unlikely(xdr_stream_decode_u32(xdr, &len) < 0)) return -EBADMSG; - if (len > SIZE_MAX / sizeof(*p)) - return -EBADMSG; - p = xdr_inline_decode(xdr, len * sizeof(*p)); + p = xdr_inline_decode(xdr, size_mul(len, sizeof(*p))); if (unlikely(!p)) return -EBADMSG; if (array == NULL)
