linux-kernel - Re: [PATCH v3] seccomp: add ptrace options for suspend/resume

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Message-ID: <20150605215208.GA27105@redhat.com>
Date:	Fri, 5 Jun 2015 23:52:08 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tycho Andersen <tycho.andersen@...onical.com>
Cc:	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	Kees Cook <keescook@...omium.org>,
	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>
Subject: Re: [PATCH v3] seccomp: add ptrace options for suspend/resume

Tycho,

I hate myself, but I have another nit ;) again, it is not that I think
you should updtate the patch, just fyi...

On 06/05, Tycho Andersen wrote:
>
> --- a/include/linux/seccomp.h
> +++ b/include/linux/seccomp.h
> @@ -95,4 +95,14 @@ static inline void get_seccomp_filter(struct task_struct *tsk)
>  	return;
>  }
>  #endif /* CONFIG_SECCOMP_FILTER */
> +
> +#ifdef CONFIG_CHECKPOINT_RESTORE
> +extern bool may_suspend_seccomp(void);
> +#else
> +static inline bool may_suspend_seccomp(void)
> +{
> +	return false;
> +}
> +#endif

This looks wrong. There is no "extern may_suspend_seccomp()" if
CONFIG_SECCOMP=n, kernel/seccomp.c is not compiled. So you need another
ifdef(CONFIG_SECCOMP).

At the same time this does not matter and you do not need the dummy
"inline" version at all:

> @@ -556,6 +557,15 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data)
>  	if (data & ~(unsigned long)PTRACE_O_MASK)
>  		return -EINVAL;
>  
> +	if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) {
> +		if (!config_enabled(CONFIG_CHECKPOINT_RESTORE) ||
> +		    !config_enabled(CONFIG_SECCOMP))
> +			return -EINVAL;
> +
> +		if (!may_suspend_seccomp())
> +			return -EPERM;

gcc will optimize out may_suspend_seccomp() unless both options are
enabled.

Oleg.

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