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Date:   Thu, 19 Oct 2017 01:42:27 +0200
From:   Christian Brauner <christian.brauner@...onical.com>
To:     kbuild test robot <lkp@...el.com>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        kbuild-all@...org, linux-kernel@...r.kernel.org,
        stgraber@...ntu.com, tycho@...ho.ws, ebiederm@...ssion.com,
        serge@...lyn.com
Subject: Re: [PATCH 1/2 v3] user namespace: use union in {g,u}idmap struct

I'm not sure why the build is complaining about how the union is initialized
here. This looks legitimate to me and I can't reproduce this locally with or
without the appended config. The struct introduced here is:

#define UID_GID_MAP_MAX_EXTENTS 5

struct uid_gid_extent {
	u32 first;
	u32 lower_first;
	u32 count;
};

struct uid_gid_map { /* 64 bytes -- 1 cache line */
	u32 nr_extents;
	union {
		struct uid_gid_extent extent[UID_GID_MAP_MAX_EXTENTS];
		struct {
			struct uid_gid_extent *forward;
			struct uid_gid_extent *reverse;
		};
	};
};

And the initialization in kernel/user.c which I didn't change looks correct.
But maybe I'm missing the point.

Christian

On Thu, Oct 19, 2017 at 06:51:48AM +0800, kbuild test robot wrote:
> Hi Christian,
> 
> [auto build test ERROR on linus/master]
> [also build test ERROR on v4.14-rc5 next-20171017]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Christian-Brauner/user-namespace-use-union-in-g-u-idmap-struct/20171019-022142
> config: x86_64-randconfig-a0-10190527 (attached as .config)
> compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
> reproduce:
>         # save the attached .config to linux build tree
>         make ARCH=x86_64 
> 
> All error/warnings (new ones prefixed by >>):
> 
> >> kernel/user.c:29: error: unknown field 'extent' specified in initializer
> >> kernel/user.c:30: error: unknown field 'first' specified in initializer
> >> kernel/user.c:30: warning: missing braces around initializer
>    kernel/user.c:30: warning: (near initialization for 'init_user_ns.uid_map.<anonymous>.extent')
> >> kernel/user.c:31: error: unknown field 'lower_first' specified in initializer
> >> kernel/user.c:31: warning: excess elements in union initializer
>    kernel/user.c:31: warning: (near initialization for 'init_user_ns.uid_map.<anonymous>')
> >> kernel/user.c:32: error: unknown field 'count' specified in initializer
>    kernel/user.c:32: warning: excess elements in union initializer
>    kernel/user.c:32: warning: (near initialization for 'init_user_ns.uid_map.<anonymous>')
>    kernel/user.c:37: error: unknown field 'extent' specified in initializer
>    kernel/user.c:38: error: unknown field 'first' specified in initializer
>    kernel/user.c:39: error: unknown field 'lower_first' specified in initializer
>    kernel/user.c:39: warning: excess elements in union initializer
>    kernel/user.c:39: warning: (near initialization for 'init_user_ns.gid_map.<anonymous>')
>    kernel/user.c:40: error: unknown field 'count' specified in initializer
>    kernel/user.c:40: warning: excess elements in union initializer
>    kernel/user.c:40: warning: (near initialization for 'init_user_ns.gid_map.<anonymous>')
>    kernel/user.c:45: error: unknown field 'extent' specified in initializer
>    kernel/user.c:46: error: unknown field 'first' specified in initializer
>    kernel/user.c:47: error: unknown field 'lower_first' specified in initializer
>    kernel/user.c:47: warning: excess elements in union initializer
>    kernel/user.c:47: warning: (near initialization for 'init_user_ns.projid_map.<anonymous>')
>    kernel/user.c:48: error: unknown field 'count' specified in initializer
>    kernel/user.c:48: warning: excess elements in union initializer
>    kernel/user.c:48: warning: (near initialization for 'init_user_ns.projid_map.<anonymous>')
> 
> vim +/lower_first +31 kernel/user.c
> 
> ^1da177e4 Linus Torvalds    2005-04-16  21  
> 59607db36 Serge E. Hallyn   2011-03-23  22  /*
> 59607db36 Serge E. Hallyn   2011-03-23  23   * userns count is 1 for root user, 1 for init_uts_ns,
> 59607db36 Serge E. Hallyn   2011-03-23  24   * and 1 for... ?
> 59607db36 Serge E. Hallyn   2011-03-23  25   */
> aee16ce73 Pavel Emelyanov   2008-02-08  26  struct user_namespace init_user_ns = {
> 22d917d80 Eric W. Biederman 2011-11-17  27  	.uid_map = {
> 22d917d80 Eric W. Biederman 2011-11-17  28  		.nr_extents = 1,
> 22d917d80 Eric W. Biederman 2011-11-17 @29  		.extent[0] = {
> 22d917d80 Eric W. Biederman 2011-11-17 @30  			.first = 0,
> 22d917d80 Eric W. Biederman 2011-11-17 @31  			.lower_first = 0,
> 4b06a81f1 Eric W. Biederman 2012-05-19 @32  			.count = 4294967295U,
> 22d917d80 Eric W. Biederman 2011-11-17  33  		},
> 22d917d80 Eric W. Biederman 2011-11-17  34  	},
> 22d917d80 Eric W. Biederman 2011-11-17  35  	.gid_map = {
> 22d917d80 Eric W. Biederman 2011-11-17  36  		.nr_extents = 1,
> 22d917d80 Eric W. Biederman 2011-11-17  37  		.extent[0] = {
> 22d917d80 Eric W. Biederman 2011-11-17  38  			.first = 0,
> 22d917d80 Eric W. Biederman 2011-11-17  39  			.lower_first = 0,
> 4b06a81f1 Eric W. Biederman 2012-05-19  40  			.count = 4294967295U,
> 22d917d80 Eric W. Biederman 2011-11-17  41  		},
> 22d917d80 Eric W. Biederman 2011-11-17  42  	},
> f76d207a6 Eric W. Biederman 2012-08-30  43  	.projid_map = {
> f76d207a6 Eric W. Biederman 2012-08-30  44  		.nr_extents = 1,
> f76d207a6 Eric W. Biederman 2012-08-30  45  		.extent[0] = {
> f76d207a6 Eric W. Biederman 2012-08-30  46  			.first = 0,
> f76d207a6 Eric W. Biederman 2012-08-30  47  			.lower_first = 0,
> f76d207a6 Eric W. Biederman 2012-08-30  48  			.count = 4294967295U,
> f76d207a6 Eric W. Biederman 2012-08-30  49  		},
> f76d207a6 Eric W. Biederman 2012-08-30  50  	},
> c61a2810a Eric W. Biederman 2012-12-28  51  	.count = ATOMIC_INIT(3),
> 783291e69 Eric W. Biederman 2011-11-17  52  	.owner = GLOBAL_ROOT_UID,
> 783291e69 Eric W. Biederman 2011-11-17  53  	.group = GLOBAL_ROOT_GID,
> 435d5f4bb Al Viro           2014-10-31  54  	.ns.inum = PROC_USER_INIT_INO,
> 33c429405 Al Viro           2014-11-01  55  #ifdef CONFIG_USER_NS
> 33c429405 Al Viro           2014-11-01  56  	.ns.ops = &userns_operations,
> 33c429405 Al Viro           2014-11-01  57  #endif
> 9cc46516d Eric W. Biederman 2014-12-02  58  	.flags = USERNS_INIT_FLAGS,
> 6bd364d82 Xiao Guangrong    2013-12-13  59  #ifdef CONFIG_PERSISTENT_KEYRINGS
> 6bd364d82 Xiao Guangrong    2013-12-13  60  	.persistent_keyring_register_sem =
> 6bd364d82 Xiao Guangrong    2013-12-13  61  	__RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
> f36f8c75a David Howells     2013-09-24  62  #endif
> aee16ce73 Pavel Emelyanov   2008-02-08  63  };
> aee16ce73 Pavel Emelyanov   2008-02-08  64  EXPORT_SYMBOL_GPL(init_user_ns);
> aee16ce73 Pavel Emelyanov   2008-02-08  65  
> 
> :::::: The code at line 31 was first introduced by commit
> :::::: 22d917d80e842829d0ca0a561967d728eb1d6303 userns: Rework the user_namespace adding uid/gid mapping support
> 
> :::::: TO: Eric W. Biederman <ebiederm@...ssion.com>
> :::::: CC: Eric W. Biederman <ebiederm@...ssion.com>
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation


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