linux-kernel - Re: [kees:seccomp/tip 2/2] kernel/ptrace.c:567:3: note: in expansion of macro 'if'

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Message-ID: <CAGXu5j+1TXE3MzbrAu=0hHgmk4nfndQxZPzi7R+oKigP21pH9Q@mail.gmail.com>
Date:	Mon, 15 Jun 2015 15:25:39 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Tycho Andersen <tycho.andersen@...onical.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>,
	Roland McGrath <roland@...k.frob.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [kees:seccomp/tip 2/2] kernel/ptrace.c:567:3: note: in expansion
 of macro 'if'

Looks like dead-code elimination happens after structures are
accessed, so this needs to use the accessor. Sorry I missed this
earlier!

I've fixed it up as:

-               if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
+               if (seccomp_mode(&current->seccomp) != SECCOMP_MODE_DISABLED ||

-Kees

On Mon, Jun 15, 2015 at 3:13 PM, kbuild test robot
<fengguang.wu@...el.com> wrote:
> tree:   git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git seccomp/tip
> head:   25234531b68b83b0a5967459613195a2ecc6b5b4
> commit: 25234531b68b83b0a5967459613195a2ecc6b5b4 [2/2] seccomp: add ptrace options for suspend/resume
> config: x86_64-randconfig-x005-201524 (attached as .config)
> reproduce:
>   git checkout 25234531b68b83b0a5967459613195a2ecc6b5b4
>   # save the attached .config to linux build tree
>   make ARCH=x86_64
>
> All warnings (new ones prefixed by >>):
>
>    In file included from include/uapi/linux/stddef.h:1:0,
>                     from include/linux/stddef.h:4,
>                     from include/uapi/linux/posix_types.h:4,
>                     from include/uapi/linux/types.h:13,
>                     from include/linux/types.h:5,
>                     from include/uapi/linux/capability.h:16,
>                     from include/linux/capability.h:15,
>                     from kernel/ptrace.c:10:
>    kernel/ptrace.c: In function 'ptrace_setoptions':
>    kernel/ptrace.c:567:23: error: 'struct seccomp' has no member named 'mode'
>       if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
>                           ^
>    include/linux/compiler.h:145:28: note: in definition of macro '__trace_if'
>      if (__builtin_constant_p((cond)) ? !!(cond) :   \
>                                ^
>>> kernel/ptrace.c:567:3: note: in expansion of macro 'if'
>       if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
>       ^
>    kernel/ptrace.c:567:23: error: 'struct seccomp' has no member named 'mode'
>       if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
>                           ^
>    include/linux/compiler.h:145:40: note: in definition of macro '__trace_if'
>      if (__builtin_constant_p((cond)) ? !!(cond) :   \
>                                            ^
>>> kernel/ptrace.c:567:3: note: in expansion of macro 'if'
>       if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
>       ^
>    kernel/ptrace.c:567:23: error: 'struct seccomp' has no member named 'mode'
>       if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
>                           ^
>    include/linux/compiler.h:156:16: note: in definition of macro '__trace_if'
>       ______r = !!(cond);     \
>                    ^
>>> kernel/ptrace.c:567:3: note: in expansion of macro 'if'
>       if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
>       ^
>
> vim +/if +567 kernel/ptrace.c
>
>    551
>    552  static int ptrace_setoptions(struct task_struct *child, unsigned long data)
>    553  {
>    554          unsigned flags;
>    555
>    556          if (data & ~(unsigned long)PTRACE_O_MASK)
>    557                  return -EINVAL;
>    558
>    559          if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
>    560                  if (!config_enabled(CONFIG_CHECKPOINT_RESTORE) ||
>    561                      !config_enabled(CONFIG_SECCOMP))
>    562                          return -EINVAL;
>    563
>    564                  if (!capable(CAP_SYS_ADMIN))
>    565                          return -EPERM;
>    566
>  > 567                  if (current->seccomp.mode != SECCOMP_MODE_DISABLED ||
>    568                      current->ptrace & PT_SUSPEND_SECCOMP)
>    569                          return -EPERM;
>    570          }
>    571
>    572          /* Avoid intermediate state when all opts are cleared */
>    573          flags = child->ptrace;
>    574          flags &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT);
>    575          flags |= (data << PT_OPT_FLAG_SHIFT);
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> http://lists.01.org/mailman/listinfo/kbuild                 Intel Corporation

-- 
Kees Cook
Chrome OS Security
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