linux-kernel - Re: [PATCH v4 2/2] ptrace, seccomp: add support for retrieving seccomp metadata

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Date:   Tue, 20 Feb 2018 22:30:52 +0300
From:   "Dmitry V. Levin" <ldv@...linux.org>
To:     Tycho Andersen <tycho@...ho.ws>
Cc:     Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...capital.net>,
        Oleg Nesterov <oleg@...hat.com>, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] ptrace, seccomp: add support for retrieving
 seccomp metadata

Hi,

On Tue, Nov 14, 2017 at 07:00:19PM -0700, Tycho Andersen wrote:
> With the new SECCOMP_FILTER_FLAG_LOG, we need to be able to extract these
> flags for checkpoint restore, since they describe the state of a filter.
> 
> So, let's add PTRACE_SECCOMP_GET_METADATA, similar to ..._GET_FILTER, which
> returns the metadata of the nth filter (right now, just the flags).
> Hopefully this will be future proof, and new per-filter metadata can be
> added to this struct.
> 
> v3: * use GET_METADATA instead of GET_FLAGS
> v4: * resend
> 
> Signed-off-by: Tycho Andersen <tycho@...ho.ws>
> CC: Kees Cook <keescook@...omium.org>
> CC: Andy Lutomirski <luto@...capital.net>
> CC: Oleg Nesterov <oleg@...hat.com>
[...]
> diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
> index e3939e00980b..e46d82b91166 100644
> --- a/include/uapi/linux/ptrace.h
> +++ b/include/uapi/linux/ptrace.h
> @@ -66,6 +66,12 @@ struct ptrace_peeksiginfo_args {
>  #define PTRACE_SETSIGMASK	0x420b
>  
>  #define PTRACE_SECCOMP_GET_FILTER	0x420c
> +#define PTRACE_SECCOMP_GET_METADATA	0x420d
> +
> +struct seccomp_metadata {
> +	unsigned long filter_off;	/* Input: which filter */
> +	unsigned int flags;		/* Output: filter's flags */
> +};

This "unsigned long" field is unacceptable unless you are willing
to implement a compat layer for this arch-dependent type.

Please use an arch-independent type instead.
See e.g. struct ptrace_peeksiginfo_args or struct struct seccomp_data.


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