From: "Serge E. Hallyn" <serge@hallyn.com>
To: Andrew Vagin <avagin@openvz.org>
Cc: linux-kernel@vger.kernel.org, criu@openvz.org,
Pavel Emelyanov <xemul@parallels.com>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Serge Hallyn <serge.hallyn@canonical.com>,
linux-security-module@vger.kernel.org,
Andrew Morgan <morgan@kernel.org>
Subject: Re: [PATCH] proc: don't show nonexistent capabilities
Date: Fri, 5 Oct 2012 14:05:19 +0000 [thread overview]
Message-ID: <20121005140519.GA28890@mail.hallyn.com> (raw)
In-Reply-To: <1349209832-279922-1-git-send-email-avagin@openvz.org>
Quoting Andrew Vagin (avagin@openvz.org):
> Without this patch it is really hard to interpret a bounding set,
> if CAP_LAST_CAP is unknown for a current kernel.
To be clear, note that you *can* figure it out using
prctl(PR_CAPBSET_DROP). But this is a nice improvement.
> Non-existant capabilities can not be deleted from a bounding set
> with help of prctl.
>
> E.g.: Here are two examples without/with this patch.
> CapBnd: ffffffe0fdecffff
> CapBnd: 00000000fdecffff
>
> I suggest to hide non-existent capabilities. Here is two reasons.
> * It's logically and easier for using.
> * It helps to checkpoint-restore capabilities of tasks, because tasks
> can be restored on another kernel, where CAP_LAST_CAP is bigger.
>
> Cc: Serge Hallyn <serge.hallyn@canonical.com>
Thanks, Andrew. I saw your other email about having run LTP, I didn't
see any problems from userspace either. Great idea!
Reviewed-by: Serge Hallyn <serge.hallyn@canonical.com>
Still it's been like that for so long that, just to be safe, I'm cc:ing
Andrew Morgan - can you see any problems with this?
> Cc: Pavel Emelyanov <xemul@parallels.com>
> Signed-off-by: Andrew Vagin <avagin@openvz.org>
> ---
> include/linux/capability.h | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/capability.h b/include/linux/capability.h
> index d10b7ed..1642778 100644
> --- a/include/linux/capability.h
> +++ b/include/linux/capability.h
> @@ -420,7 +420,8 @@ extern const kernel_cap_t __cap_init_eff_set;
> #else /* HAND-CODED capability initializers */
>
> # define CAP_EMPTY_SET ((kernel_cap_t){{ 0, 0 }})
> -# define CAP_FULL_SET ((kernel_cap_t){{ ~0, ~0 }})
> +# define CAP_FULL_SET ((kernel_cap_t){{ ~0, \
> + CAP_TO_MASK(CAP_LAST_CAP + 1) - 1 } })
> # define CAP_FS_SET ((kernel_cap_t){{ CAP_FS_MASK_B0 \
> | CAP_TO_MASK(CAP_LINUX_IMMUTABLE), \
> CAP_FS_MASK_B1 } })
> --
> 1.7.1
>
> --
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next prev parent reply other threads:[~2012-10-05 14:03 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-02 20:30 [PATCH] proc: don't show nonexistent capabilities Andrew Vagin
2012-10-03 16:24 ` Serge E. Hallyn
2012-10-04 21:42 ` Andrey Wagin
2012-10-05 14:05 ` Serge E. Hallyn [this message]
2012-10-05 15:54 ` Andrew G. Morgan
2012-10-05 16:46 ` Serge Hallyn
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