Re: [PATCH 12/15] Manual pages: cap_get_file.3: NOTES: note the effect of the Ambient set

From: "Andrew G. Morgan" <morgan@kernel.org>
To: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: LSM List <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH 12/15] Manual pages: cap_get_file.3: NOTES: note the effect of the Ambient set
Date: Mon, 20 Jul 2020 08:36:10 -0700	[thread overview]
Message-ID: <CALQRfL5-aL3h6M+CYqkVHSpPKQ-i3s+RWD8060AicrGPP3vSfw@mail.gmail.com> (raw)
In-Reply-To: <20200720091328.290336-13-mtk.manpages@gmail.com>

I've applied all but this one. This one seems to imply that if the
effective bit is lowered, but the permitted bits are raised, the
ambient will have some sort of effect. This isn't how it works. Any
file caps (even an empty set) suppresses any effect of the ambient
vector.

Cheers

Andrew

On Mon, Jul 20, 2020 at 2:14 AM Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
>
> The addition of Ambient capabilities in Linux 4.3 rendered the text on
> the effect of the Effective bit during execve(2) out-of-date. Fix that.
> Also add a couple of paragraph breaks to improve readability.
>
> Signed-off-by: Michael Kerrisk (man-pages) <mtk.manpages@gmail.com>
> ---
>  doc/cap_get_file.3 | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/doc/cap_get_file.3 b/doc/cap_get_file.3
> index ceacbaf..dc7b571 100644
> --- a/doc/cap_get_file.3
> +++ b/doc/cap_get_file.3
> @@ -103,13 +103,18 @@ or
>  These functions are specified by withdrawn POSIX.1e draft specification.
>  .SH NOTES
>  Support for file capabilities is provided on Linux since version 2.6.24.
> -
> +.PP
>  On Linux, the file Effective set is a single bit.
>  If it is enabled, then all Permitted capabilities are enabled
>  in the Effective set of the calling process when the file is executed;
> -otherwise, no capabilities are enabled in the process's Effective set
> +otherwise, the process's Ambient capabilities
> +(or, before the Linux 4.3 addition of Ambient capabilities, no capabilities)
> +are enabled in the process's Effective set
>  following an
> -.BR execve (2).
> +.BR execve (2)
> +(see
> +.BR capabilities (7)).
> +.PP
>  Because the file Effective set is a single bit,
>  if any capability is enabled in the Effective set of the
>  .I cap_t
> --
> 2.26.2
>