linux-kernel - Re: [PATCH 14/15] selftests/clone3: Avoid OS-defined clone

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Date:   Tue, 15 Sep 2020 18:25:28 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christian Brauner <christian@...uner.io>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        linux-kselftest@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org,
        linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 14/15] selftests/clone3: Avoid OS-defined clone_args

On Sat, Sep 12, 2020 at 04:08:19AM -0700, Kees Cook wrote:
> As the UAPI headers start to appear in distros, we need to avoid
> outdated versions of struct clone_args to be able to test modern
> features. Additionally pull in the syscall numbers correctly.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---

Hm, with this patch applied I'm getting:

gcc -g -I../../../../usr/include/    clone3_set_tid.c /home/brauner/src/git/linux/linux/tools/testing/selftests/kselftest_harness.h /home/brauner/src/git/linux/linux/tools/testing/selftests/kselftest.h -lcap -o /home/brauner/src/git/linux/linux/tools/testing/selftests/clone3/clone3_set_tid
In file included from clone3_set_tid.c:24:
clone3_selftests.h:37:8: error: redefinition of ‘struct clone_args’
   37 | struct clone_args {
      |        ^~~~~~~~~~
In file included from clone3_set_tid.c:12:
/usr/include/linux/sched.h:92:8: note: originally defined here
   92 | struct clone_args {
      |        ^~~~~~~~~~
make: *** [../lib.mk:140: /home/brauner/src/git/linux/linux/tools/testing/selftests/clone3/clone3_set_tid] Error 1

One trick to avoid this could be:

#ifndef CLONE_ARGS_SIZE_VER0
#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
#endif

#ifndef CLONE_ARGS_SIZE_VER1
#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
#endif

#ifndef CLONE_ARGS_SIZE_VER2
#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
#endif

struct __clone_args {
	__aligned_u64 flags;
	__aligned_u64 pidfd;
	__aligned_u64 child_tid;
	__aligned_u64 parent_tid;
	__aligned_u64 exit_signal;
	__aligned_u64 stack;
	__aligned_u64 stack_size;
	__aligned_u64 tls;
	__aligned_u64 set_tid;
	__aligned_u64 set_tid_size;
	__aligned_u64 cgroup;
};

static pid_t sys_clone3(struct __clone_args *args, size_t size)
{
	return syscall(__NR_clone3, args, size);
}

Christian