Re: Aufs support for Linux User namespace
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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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 -- See everything from the browser to the database with AppDynamics Get end-to-end visibility with application monitoring from AppDynamics Isolate bottlenecks and diagnose root cause in seconds. Start your free trial of AppDynamics Pro today! http://pubads.g.doubleclick.net/gampad/clk?id=48808831iu=/4140/ostg.clktrk
RE: Aufs support for Linux User namespace
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 -- See everything from the browser to the database with AppDynamics Get end-to-end visibility with application monitoring from AppDynamics Isolate bottlenecks and diagnose root cause in seconds. Start your free trial of AppDynamics Pro today! http://pubads.g.doubleclick.net/gampad/clk?id=48808831iu=/4140/ostg.clktrk
Re: Aufs support for Linux User namespace
Hello Bhushan, Bhushan Jain: Linux kernel 3.8 has added support for user namespace which allows unprivileged users to create different namespaces for sandboxing within the user namespace. The filesystem developers need to explicitly allow mounting their filesystem types within a user namespace. This explicit permission is required because an overall unprivileged user of the system can be mapped to a root user within a user namespace. Most of the Linux filesystems already support user namespaces. If you can, please provide me - sample usage of user-namespace - sample case where user-namespace and aufs is beneficial This use namespace support can be added by a small change in the file fs/aufs/super.c to add flag FS_USERNS_MOUNT to aufs_fs_type (shown in bold below). Please let me know if you would like me to send a patch including this change. The change is apparently small, but the patch is better because it will record your name in the git history. Just out of curiosity, do you know any recent activity on Unionfs? J. R. Okajima -- See everything from the browser to the database with AppDynamics Get end-to-end visibility with application monitoring from AppDynamics Isolate bottlenecks and diagnose root cause in seconds. Start your free trial of AppDynamics Pro today! http://pubads.g.doubleclick.net/gampad/clk?id=48808831iu=/4140/ostg.clktrk
