linux-kernel - Re: [PATCH net-next v7 05/10] landlock: Add LSM hooks related to filesystem

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Message-ID: <753a3a91-23a4-bc63-27cb-12e764d3d5fc@digikod.net>
Date:   Tue, 22 Aug 2017 23:59:33 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     linux-kernel@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Drysdale <drysdale@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        James Morris <james.l.morris@...cle.com>,
        Jann Horn <jann@...jh.net>, Jonathan Corbet <corbet@....net>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Moore <paul@...l-moore.com>,
        Sargun Dhillon <sargun@...gun.me>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Shuah Khan <shuah@...nel.org>, Tejun Heo <tj@...nel.org>,
        Thomas Graf <tgraf@...g.ch>, Will Drewry <wad@...omium.org>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-security-module@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v7 05/10] landlock: Add LSM hooks related to
 filesystem


On 21/08/2017 02:09, Mickaël Salaün wrote:
> Handle 33 filesystem-related LSM hooks for the Landlock filesystem
> event: LANDLOCK_SUBTYPE_EVENT_FS.
> 
> A Landlock event wrap LSM hooks for similar kernel object types (e.g.
> struct file, struct path...). Multiple LSM hooks can trigger the same
> Landlock event.
> 
> Landlock handle nine coarse-grained actions: read, write, execute, new,
> get, remove, ioctl, lock and fcntl. Each of them abstract LSM hook
> access control in a way that can be extended in the future.
> 
> The Landlock LSM hook registration is done after other LSM to only run
> actions from user-space, via eBPF programs, if the access was granted by
> major (privileged) LSMs.
> 
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: James Morris <james.l.morris@...cle.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Serge E. Hallyn <serge@...lyn.com>
> ---
> 
> Changes since v6:
> * add 3 more sub-events: IOCTL, LOCK, FCNTL
>   https://lkml.kernel.org/r/2fbc99a6-f190-f335-bd14-04bdeed35571@digikod.net
> * use the new security_add_hooks()
> * explain the -Werror=unused-function
> * constify pointers
> * cleanup headers
> 
> Changes since v5:
> * split hooks.[ch] into hooks.[ch] and hooks_fs.[ch]
> * add more documentation
> * cosmetic fixes
> * rebase (SCALAR_VALUE)
> 
> Changes since v4:
> * add LSM hook abstraction called Landlock event
>   * use the compiler type checking to verify hooks use by an event
>   * handle all filesystem related LSM hooks (e.g. file_permission,
>     mmap_file, sb_mount...)
> * register BPF programs for Landlock just after LSM hooks registration
> * move hooks registration after other LSMs
> * add failsafes to check if a hook is not used by the kernel
> * allow partial raw value access form the context (needed for programs
>   generated by LLVM)
> 
> Changes since v3:
> * split commit
> * add hooks dealing with struct inode and struct path pointers:
>   inode_permission and inode_getattr
> * add abstraction over eBPF helper arguments thanks to wrapping structs
> ---
>  include/linux/lsm_hooks.h    |   5 +
>  security/landlock/Makefile   |   7 +-
>  security/landlock/common.h   |   2 +
>  security/landlock/hooks.c    |  83 ++++++
>  security/landlock/hooks.h    | 177 +++++++++++++
>  security/landlock/hooks_fs.c | 586 +++++++++++++++++++++++++++++++++++++++++++
>  security/landlock/hooks_fs.h |  19 ++
>  security/landlock/init.c     |  10 +
>  security/security.c          |  12 +-
>  9 files changed, 899 insertions(+), 2 deletions(-)
>  create mode 100644 security/landlock/hooks.c
>  create mode 100644 security/landlock/hooks.h
>  create mode 100644 security/landlock/hooks_fs.c
>  create mode 100644 security/landlock/hooks_fs.h

> diff --git a/security/landlock/init.c b/security/landlock/init.c
> index 09acbc74abd6..1e6660fed697 100644
> --- a/security/landlock/init.c
> +++ b/security/landlock/init.c
> @@ -10,8 +10,10 @@
>  
>  #include <linux/bpf.h> /* enum bpf_access_type */
>  #include <linux/capability.h> /* capable */
> +#include <linux/lsm_hooks.h>
>  
>  #include "common.h" /* LANDLOCK_* */
> +#include "hooks_fs.h"
>  
>  
>  static inline bool bpf_landlock_is_valid_access(int off, int size,
> @@ -23,6 +25,8 @@ static inline bool bpf_landlock_is_valid_access(int off, int size,
>  
>  	switch (prog_subtype->landlock_rule.event) {
>  	case LANDLOCK_SUBTYPE_EVENT_FS:
> +		return landlock_is_valid_access_event_FS(off, size, type,
> +				&info->reg_type, prog_subtype);

I forgot to handle LANDLOCK_SUBTYPE_EVENT_FS_{IOCTL,LOCK_FCNTL} here and
I included some hunks in the wrong patches. I will fix this in the next
series and add tests for those anyway. :)

Regards,
 Mickaël



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