linux-kernel - Re: [RESEND][RFC][PATCH 1/3] lsm: Clarify documentation of vm_enough

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Message-ID: <CACYkzJ5nwsdaG57HHkNubPptkB=_Mz68TVzmX8+Tg=ZFjMX3pw@mail.gmail.com>
Date:   Thu, 3 Nov 2022 16:11:13 +0100
From:   KP Singh <kpsingh@...nel.org>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, sdf@...gle.com, haoluo@...gle.com,
        jolsa@...nel.org, mykolal@...com, revest@...omium.org,
        jackmanb@...omium.org, shuah@...nel.org, paul@...l-moore.com,
        casey@...aufler-ca.com, zohar@...ux.ibm.com, bpf@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, nicolas.bouchinet@...p-os.org
Subject: Re: [RESEND][RFC][PATCH 1/3] lsm: Clarify documentation of
 vm_enough_memory hook

On Fri, Oct 28, 2022 at 6:55 PM Roberto Sassu
<roberto.sassu@...weicloud.com> wrote:
>
> From: Roberto Sassu <roberto.sassu@...wei.com>
>
> include/linux/lsm_hooks.h reports the result of the LSM infrastructure to
> the callers, not what LSMs should return to the LSM infrastructure.
>
> Clarify that and add that returning 1 from the LSMs means calling
> __vm_enough_memory() with cap_sys_admin set, 0 without.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>

Reviewed-by: KP Singh <kpsingh@...nel.org>

> ---
>  include/linux/lsm_hooks.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 4ec80b96c22e..f40b82ca91e7 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1411,7 +1411,9 @@
>   *     Check permissions for allocating a new virtual mapping.
>   *     @mm contains the mm struct it is being added to.
>   *     @pages contains the number of pages.
> - *     Return 0 if permission is granted.
> + *     Return 0 if permission is granted by LSMs to the caller. LSMs should
> + *     return 1 if __vm_enough_memory() should be called with
> + *     cap_sys_admin set, 0 if not.
>   *
>   * @ismaclabel:
>   *     Check if the extended attribute specified by @name
> --
> 2.25.1
>