Hi Junjiro,
I converted Bhushan Jain's changes into a git patch, so you can easy
apply it to your tree.
Florian
Am 17.07.2013 23:58, schrieb Bhushan Jain:
> Hi,
> Thanks for letting me know about this discussion.
> Serge is correct. By allowing this flag, an un-privileged user can mount aufs
> filesystem within the user namespace and the administrator needs to be aware
> of this. However, I am not sure about the harm in letting an unprivileged
> user mount the aufs filesystem. The file permissions cannot be violated even
> in a user namespace.
>
> As Eric said:
> "The rule with filesystems like that is mounting them needs to be no more
> dangerous than bind mounting them."
>
> And I think, this is true for aufs filesystem. Please correct me if I am
> wrong.
>
> Thanks,
> Bhushan
> ________________________________________
> From: sf...@users.sourceforge.net [sf...@users.sourceforge.net]
> Sent: Wednesday, July 17, 2013 9:57 AM
> To: Bhushan Jain; aufs-users@lists.sourceforge.net
> Subject: Re: Aufs support for Linux User namespace
>
> sf...@users.sourceforge.net:
>> Bhushan Jain:
>>> Attached is a sample code that creates a user namespace and maps the un-pri=
>>> vileged user to root within the namespace.=0A=
>>> The user namespace can be used for sandboxing. Having aufs support within t=
>>> he user namespace can help create a chroot environment where multiple direc=
>>> tories are united into a single filesystem.=0A=
>> Thanks for the sample code.
>> Personally, user-ns is not attractive for me, at the same time I don't
>> have strong objection. So I will merge your patch.
> Intrestingly, very similar discussion happened on LKML.
> See this and its thread.
> Date: Tue, 16 Jul 2013 14:29:20 -0500
> From: Serge Hallyn <serge.hal...@ubuntu.com>
> Subject: [PATCH RFC] allow some kernel filesystems to be mounted
> in a user namespace
>
> The patch sets FS_USERNS_MOUNT for debugfs, fuse and securityfs.
> But at the end of the thread, he wrote
> Right so the specific problem this patch introduces is: An admin who
> is
> using a distro kernel with these filesystems enabled but not mounted,
> without this patch does not have to worry about unprivileged users
> being
> able to access the fs. With this patch, he does.
>
> Thanks everyone, I withdraw this patch.
>
> If such problem really exists, it might be better for aufs NOT to set
> FS_USERNS_MOUNT I suppose.
>
>
> J. R. Okajima
>
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>From 205fb5d18bb77c60b155808658e1ef146d0a2c8a Mon Sep 17 00:00:00 2001
From: Bhushan Jain <bpj...@cs.stonybrook.edu>
Date: Wed, 25 Sep 2013 11:15:14 +0200
Subject: [PATCH] aufs: add support for user namespaces
---
fs/aufs/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/aufs/super.c b/fs/aufs/super.c
index 4f57ba0..be39ce4 100644
--- a/fs/aufs/super.c
+++ b/fs/aufs/super.c
@@ -984,7 +984,7 @@ static void aufs_kill_sb(struct super_block *sb)
struct file_system_type aufs_fs_type = {
.name = AUFS_FSTYPE,
/* a race between rename and others */
- .fs_flags = FS_RENAME_DOES_D_MOVE,
+ .fs_flags = FS_RENAME_DOES_D_MOVE | FS_USERNS_MOUNT,
.mount = aufs_mount,
.kill_sb = aufs_kill_sb,
/* no need to __module_get() and module_put(). */
--
1.8.4
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