linux-kernel - [PATCH] sunrpc: avoid constant-out-of-range warning with clang

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Date:   Mon,  3 Jul 2023 13:37:22 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Neil Brown <neilb@...e.de>,
        Olga Kornievskaia <kolga@...app.com>,
        Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Dan Carpenter <error27@...il.com>,
        linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: [PATCH] sunrpc: avoid constant-out-of-range warning with clang

From: Arnd Bergmann <arnd@...db.de>

The overflow check in xdr_stream_decode_uint32_array() was added for
32-bit systems, but on 64-bit builds it causes a build warning when
building with clang and W=1:

In file included from init/do_mounts.c:22:
include/linux/sunrpc/xdr.h:778:10: error: result of comparison of constant 4611686018427387903 with expression of type '__u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
  778 |         if (len > SIZE_MAX / sizeof(*p))

Shut up the warning with a type cast.

Fixes: 23a9dbbe0faf1 ("NFSD: prevent integer overflow on 32 bit systems")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 include/linux/sunrpc/xdr.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index f89ec4b5ea169..6736121ee6a03 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -775,7 +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))
+	if ((size_t)len > SIZE_MAX / sizeof(*p))
 		return -EBADMSG;
 	p = xdr_inline_decode(xdr, len * sizeof(*p));
 	if (unlikely(!p))
-- 
2.39.2