[PATCH 02/10] vfs: syscall: Add move_mount(2) to move mounts around

[Tetsuo Handa]

I did not see AppArmor patch for this problem in 5.3-rc1. 
John, are you OK with this patch for 5.2-stable and 5.3 ?

On 2019/07/09 19:51, Tetsuo Handa wrote:
> For now, can we apply this patch for 5.2-stable ?
> 
> 
>>From dd62fab0592e02580fd5a34222a2d11bfc179f61 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
> Date: Tue, 9 Jul 2019 19:05:49 +0900
> Subject: [PATCH] LSM: Disable move_mount() syscall when TOMOYO or AppArmor is enabled.
> 
> Commit 2db154b3ea8e14b0 ("vfs: syscall: Add move_mount(2) to move mounts
> around") introduced security_move_mount() LSM hook, but we missed that
> TOMOYO and AppArmor did not implement hooks for checking move_mount(2).
> For pathname based access controls like TOMOYO and AppArmor, unchecked
> mount manipulation is not acceptable. Therefore, until TOMOYO and AppArmor
> implement hooks, in order to avoid unchecked mount manipulation, pretend
> as if move_mount(2) is unavailable when either TOMOYO or AppArmor is
> enabled.
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
> Fixes: 2db154b3ea8e14b0 ("vfs: syscall: Add move_mount(2) to move mounts around")
> Cc: stable at vger.kernel.org # 5.2
> ---
>  include/linux/lsm_hooks.h | 6 ++++++
>  security/apparmor/lsm.c   | 1 +
>  security/tomoyo/tomoyo.c  | 1 +
>  3 files changed, 8 insertions(+)
> 
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 47f58cf..cd411b7 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -2142,4 +2142,10 @@ static inline void security_delete_hooks(struct security_hook_list *hooks,
>  
>  extern int lsm_inode_alloc(struct inode *inode);
>  
> +static inline int no_move_mount(const struct path *from_path,
> +				const struct path *to_path)
> +{
> +	return -ENOSYS;
> +}
> +
>  #endif /* ! __LINUX_LSM_HOOKS_H */
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index ec3a928..5cdf63b 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -1158,6 +1158,7 @@ struct lsm_blob_sizes apparmor_blob_sizes __lsm_ro_after_init = {
>  	LSM_HOOK_INIT(capable, apparmor_capable),
>  
>  	LSM_HOOK_INIT(sb_mount, apparmor_sb_mount),
> +	LSM_HOOK_INIT(move_mount, no_move_mount),
>  	LSM_HOOK_INIT(sb_umount, apparmor_sb_umount),
>  	LSM_HOOK_INIT(sb_pivotroot, apparmor_sb_pivotroot),
>  
> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
> index 716c92e..be1b1a1 100644
> --- a/security/tomoyo/tomoyo.c
> +++ b/security/tomoyo/tomoyo.c
> @@ -558,6 +558,7 @@ static void tomoyo_task_free(struct task_struct *task)
>  	LSM_HOOK_INIT(path_chown, tomoyo_path_chown),
>  	LSM_HOOK_INIT(path_chroot, tomoyo_path_chroot),
>  	LSM_HOOK_INIT(sb_mount, tomoyo_sb_mount),
> +	LSM_HOOK_INIT(move_mount, no_move_mount),
>  	LSM_HOOK_INIT(sb_umount, tomoyo_sb_umount),
>  	LSM_HOOK_INIT(sb_pivotroot, tomoyo_sb_pivotroot),
>  	LSM_HOOK_INIT(socket_bind, tomoyo_socket_bind),
>