linux-kernel - Re: [PATCH v2 1/2] lsm: Clarify documentation of vm_enough

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Message-ID: <CAHC9VhTuEH83tcA-Je7NMkxF8a1W=Bg+oLhLYeASKp70VqAy4w@mail.gmail.com>
Date:   Tue, 6 Dec 2022 17:51:27 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>
Cc:     casey@...aufler-ca.com, omosnace@...hat.com,
        john.johansen@...onical.com, kpsingh@...nel.org,
        bpf@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v2 1/2] lsm: Clarify documentation of vm_enough_memory hook

On Mon, Nov 28, 2022 at 9:43 AM 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 if all LSMs return a positive value
> __vm_enough_memory() will be called with cap_sys_admin set. If at least one
> LSM returns 0 or negative, it will be called with cap_sys_admin cleared.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
>  include/linux/lsm_hooks.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

Thanks Roberto.  Normally I don't like merging patches this close to
the merge window, but as this is a comment-only fix that makes an
important clarification I'm going to make an exception here and merge
it into lsm/next.

> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 2831efebde69..c35e260efd8c 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1398,7 +1398,11 @@
>   *     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 the LSM infrastructure to the
> + *     caller. If all LSMs return a positive value, __vm_enough_memory() will
> + *     be called with cap_sys_admin set. If at least one LSM returns 0 or
> + *     negative, __vm_enough_memory() will be called with cap_sys_admin
> + *     cleared.
>   *
>   * @ismaclabel:
>   *     Check if the extended attribute specified by @name
> --
> 2.25.1

-- 
paul-moore.com