linux-kernel - Re: [PATCH] y2038: fix socket.h header inclusion

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Message-ID: <87a7hvded7.fsf@mid.deneb.enyo.de>
Date:   Fri, 15 Mar 2019 22:20:04 +0100
From:   Florian Weimer <fw@...eb.enyo.de>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Willem de Bruijn <willemb@...gle.com>,
        alpha <linux-alpha@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-mips@...r.kernel.org,
        Parisc List <linux-parisc@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>,
        Networking <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH] y2038: fix socket.h header inclusion

* Arnd Bergmann:

> On Thu, Mar 14, 2019 at 7:41 PM Florian Weimer <fw@...eb.enyo.de> wrote:
>>
>> * Arnd Bergmann:
>>
>> > diff --git a/arch/alpha/include/uapi/asm/socket.h
>> > b/arch/alpha/include/uapi/asm/socket.h
>> > index 0d0fddb7e738..976e89b116e5 100644
>> > --- a/arch/alpha/include/uapi/asm/socket.h
>> > +++ b/arch/alpha/include/uapi/asm/socket.h
>> > @@ -2,8 +2,8 @@
>> >  #ifndef _UAPI_ASM_SOCKET_H
>> >  #define _UAPI_ASM_SOCKET_H
>> >
>> > +#include <linux/posix_types.h>
>> >  #include <asm/sockios.h>
>> > -#include <asm/bitsperlong.h>
>>
>> This breaks POSIX conformance in glibc because the
>> <linux/posix_types.h> header is not namespace clean.  It contains the
>> identifiers fds_bits and val:
>>
>>         unsigned long fds_bits[__FD_SETSIZE / (8 * sizeof(long))];
>>
>>         int     val[2];
>
> What is problematic about the struct members here? I had thought that
> only the struct names have to be in a namespace to be usable here,
> but not the members.

According POSIX, a user can do this:

#define fds_bits 1024

before including the <sys/socket.h> header file.  Similarly for val.

Since glibc pulls in <asm/socket.h> indirectly, the result is a parse
error, even though the programmer did nothing wrong (fds_bits is not
an identifier used by POSIX, nor is it in the implementation
namespace, ans <sys/socket.h> is a POSIX header).

> We could use asm/posix_types.h instead of linux/posix_types.h,
> would that address your concern?

It should fix the fds_bits case, I think.  But
<asm-generic/posix_types.h> still uses val, so that part of the issue
remains.