linux-kernel - Re: [patch] seccomp.2: Note that memory area is read-only

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Date:	Sat, 18 Apr 2015 13:17:28 +0200
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	"CC: Kees Cook" <keescook@...omium.org>
Cc:	Michael Kerrisk <mtk.manpages@...il.com>,
	"linux-man@...r.kernel.org" <linux-man@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [patch] seccomp.2: Note that memory area is read-only

Hi Kees,

Ping!

Cheers,

Michael



On 6 April 2015 at 17:29, Michael Kerrisk (man-pages)
<mtk.manpages@...il.com> wrote:
> Hi Kees,
>
> I recently was asked about the point below, and had to go check the code
> to be sure, since the man page said nothing. It would be good to have
> a confirmation: the seccomp_data buffer supplied to a seccomp BPF program
> is read-only, right? (That is, one can't write to the buffer in order to
> change the arguments that a system call actually receives.)
>
> A small man page patch below.
>
> Cheers,
>
> Michael
>
> --- a/man2/seccomp.2
> +++ b/man2/seccomp.2
> @@ -232,15 +232,15 @@ struct sock_filter {            /* Filter block */
>  };
>  .fi
>  .in
>
>  When executing the instructions, the BPF program operates on the
>  system call information made available (i.e., use the
>  .BR BPF_ABS
> -addressing mode) as a buffer of the following form:
> +addressing mode) as a (read-only) buffer of the following form:
>
>  .in +4n
>  .nf
>  struct seccomp_data {
>      int   nr;                   /* System call number */
>      __u32 arch;                 /* AUDIT_ARCH_* value
>                                     (see <linux/audit.h>) */
>
>
> --
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Linux/UNIX System Programming Training: http://man7.org/training/



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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