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

From: John Johansen <john.johansen@canonical.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	David Howells <dhowells@redhat.com>,
	linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	torvalds@linux-foundation.org,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH 02/10] vfs: syscall: Add move_mount(2) to move mounts around
Date: Mon, 22 Jul 2019 21:16:49 -0700	[thread overview]
Message-ID: <e75d4a66-cfcf-2ce8-e82a-fdc80f01723d@canonical.com> (raw)
In-Reply-To: <1698ec76-f56c-1e65-2f11-318c0ed225bb@i-love.sakura.ne.jp>

On 7/22/19 3:12 AM, Tetsuo Handa wrote:
> 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 ?
> 
yes, I have some larger mount rework and clean-up to do and an apparmor
patch for this is waiting on that. Looking at the thread I am wondering
where my previous reply is, probably lost in a mail client crash, I have
had a few of those lately.

Acked-by: John Johansen <john.johansen@canonical.com>


> 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@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@I-love.SAKURA.ne.jp>
>> Fixes: 2db154b3ea8e14b0 ("vfs: syscall: Add move_mount(2) to move mounts around")
>> Cc: stable@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),
>>
>