From: Kees Cook <keescook@chromium.org>
To: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/1] samples/seccomp: eliminate two compile warnings in user-trap.c
Date: Tue, 8 Sep 2020 16:42:37 -0700 [thread overview]
Message-ID: <202009081633.CC35635@keescook> (raw)
In-Reply-To: <973a1752-7609-bac9-758a-1a977e6fb1f0@huawei.com>
On Wed, Sep 02, 2020 at 09:33:06AM +0800, Leizhen (ThunderTown) wrote:
> On 2020/9/1 16:39, Zhen Lei wrote:
> > samples/seccomp/user-trap.c is compiled with $(userccflags), and the
> > latter does not contain -fno-strict-aliasing, so the warnings reported as
> > below. Due to add "userccflags += -fno-strict-aliasing" will impact other
> > files, so use __attribute__((__may_alias__)) to suppress it exactly.
> >
> > My gcc version is 5.5.0 20171010.
> >
> > ----------
> > samples/seccomp/user-trap.c: In function ‘send_fd’:
> > samples/seccomp/user-trap.c:50:2: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
> > *((int *)CMSG_DATA(cmsg)) = fd;
> > ^
> > samples/seccomp/user-trap.c: In function ‘recv_fd’:
> > samples/seccomp/user-trap.c:83:2: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
> > return *((int *)CMSG_DATA(cmsg));
> > ^
>
> Doesn't anyone care about this? Or is it that everyone hasn't encountered this problem?
> Why do these two warnings occur every time I compiled?
Hi!
I think the samples have been a bit ignored lately because they have a
lot of weird build issues with regard to native vs compat and needing
the kernel headers to be built first, etc.
That said, yes, I'd like to fix warnings. However, I can't reproduce
this. How are you building? I tried x86_64 and cross-compiled to i386.
--
Kees Cook
next prev parent reply other threads:[~2020-09-08 23:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 8:39 [PATCH v2 0/1] samples/seccomp: eliminate two compile warnings in user-trap.c Zhen Lei
2020-09-01 8:39 ` [PATCH v2 1/1] " Zhen Lei
2020-09-02 1:33 ` Leizhen (ThunderTown)
2020-09-08 23:42 ` Kees Cook [this message]
2020-09-09 2:20 ` Leizhen (ThunderTown)
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