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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Fri, 7 Jul 2023 14:50:23 -0700
Message-ID: <CAKwvOdmedTDChYYSgdC0LQGOdrzm1ua--kUcz-KGXi4TnxcvUg@mail.gmail.com>
Subject: Re: [PATCH] sunrpc: avoid constant-out-of-range warning with clang
To:     Dan Carpenter <dan.carpenter@linaro.org>,
        Arnd Bergmann <arnd@kernel.org>
Cc:     Chuck Lever <chuck.lever@oracle.com>,
        Jeff Layton <jlayton@kernel.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Neil Brown <neilb@suse.de>,
        Olga Kornievskaia <kolga@netapp.com>,
        Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Tom Rix <trix@redhat.com>, Dan Carpenter <error27@gmail.com>,
        linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev
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On Mon, Jul 3, 2023 at 5:42=E2=80=AFAM Dan Carpenter <dan.carpenter@linaro.=
org> wrote:
>
> On Mon, Jul 03, 2023 at 01:37:22PM +0200, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.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=3D1:
> >
> > In file included from init/do_mounts.c:22:
> > include/linux/sunrpc/xdr.h:778:10: error: result of comparison of const=
ant 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@arndb.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 *x=
dr,
> >
> >       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 =3D xdr_inline_decode(xdr, len * sizeof(*p));
>
> I sent a patch for this last week that takes a different approach.
>
> https://lore.kernel.org/all/2390fdc8-13fa-4456-ab67-44f0744db412@moroto.m=
ountain/
>
> I probably should have used a Fixes tag just for informational purposes.

I have a slight preference for retaining the existing error handling
here, but am happy to have 2 fixes in hand rather than 0; thank you
both for your time looking at this.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>
> regards,
> dan carpenter
>


--=20
Thanks,
~Nick Desaulniers