netdev - Re: [PATCH v4 7/20] lsm: Refactor return value of LSM hook setprocattr

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Message-ID: <dc54d44a-465a-472c-8636-5de786ad0264@huaweicloud.com>
Date: Sat, 20 Jul 2024 17:31:44 +0800
From: Xu Kuohai <xukuohai@...weicloud.com>
To: Paul Moore <paul@...l-moore.com>, bpf@...r.kernel.org,
 netdev@...r.kernel.org, linux-security-module@...r.kernel.org,
 linux-kselftest@...r.kernel.org, linux-integrity@...r.kernel.org,
 selinux@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
 Matt Bobrowski <mattbobrowski@...gle.com>,
 Brendan Jackman <jackmanb@...omium.org>, James Morris <jmorris@...ei.org>,
 "Serge E . Hallyn" <serge@...lyn.com>,
 Khadija Kamran <kamrankhadijadj@...il.com>,
 Casey Schaufler <casey@...aufler-ca.com>,
 Ondrej Mosnacek <omosnace@...hat.com>, Kees Cook <keescook@...omium.org>,
 John Johansen <john.johansen@...onical.com>,
 Lukas Bulwahn <lukas.bulwahn@...il.com>,
 Roberto Sassu <roberto.sassu@...wei.com>,
 Shung-Hsi Yu <shung-hsi.yu@...e.com>, Edward Cree <ecree.xilinx@...il.com>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>,
 Trond Myklebust <trond.myklebust@...merspace.com>,
 Anna Schumaker <anna@...nel.org>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Stephen Smalley <stephen.smalley.work@...il.com>
Subject: Re: [PATCH v4 7/20] lsm: Refactor return value of LSM hook
 setprocattr

On 7/19/2024 10:08 AM, Paul Moore wrote:
> On Jul 11, 2024 Xu Kuohai <xukuohai@...weicloud.com> wrote:
>>
>> To be consistent with most LSM hooks, convert the return value of
>> hook setprocattr to 0 or a negative error code.
>>
>> Before:
>> - Hook setprocattr returns the number of bytes written on success
>>    or a negative error code on failure.
>>
>> After:
>> - Hook setprocattr returns 0 on success or a negative error code
>>    on failure. An output parameter @wbytes is introduced to hold
>>    the number of bytes written on success.
>>
>> Signed-off-by: Xu Kuohai <xukuohai@...wei.com>
>> ---
>>   fs/proc/base.c                |  5 +++--
>>   include/linux/lsm_hook_defs.h |  3 ++-
>>   include/linux/security.h      |  5 +++--
>>   security/apparmor/lsm.c       | 10 +++++++---
>>   security/security.c           |  8 +++++---
>>   security/selinux/hooks.c      | 11 ++++++++---
>>   security/smack/smack_lsm.c    | 14 ++++++++++----
>>   7 files changed, 38 insertions(+), 18 deletions(-)
> 
> The security_setprocattr() hook is another odd case that we probably
> just want to leave alone for two reasons:
> 
> 1. With the move to LSM syscalls for getting/setting a task's LSM
> attributes we are "freezing" the procfs API and not adding any new
> entries to it.
> 
> 2. The BPF LSM doesn't currently register any procfs entries.
> 
> I'd suggest leaving security_setprocattr() as-is and blocking it in
> the BPF verifier, I can't see any reason why a BPF LSM would need
> this hook.
> 
OK, I'll drop this patch in the next version.