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From: Cedric Le Goater <clg@fr.ibm.com>
To: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: Andrew Morton <akpm@osdl.org>, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -mm 7/8] user_ns: handle file sigio
Date: Mon, 15 Jan 2007 16:03:49 +0100	[thread overview]
Message-ID: <45AB97D5.6010503@fr.ibm.com> (raw)
In-Reply-To: <20070115072653.GA7385@sergelap.austin.ibm.com>

Serge E. Hallyn wrote:
> Quoting Andrew Morton (akpm@osdl.org):
>> On Thu, 4 Jan 2007 12:12:57 -0600
>> "Serge E. Hallyn" <serue@us.ibm.com> wrote:
>>
>>> A process in one user namespace could set a fowner and sigio on a file in a
>>> shared vfsmount, ending up killing a task in another user namespace.
>>>
>>> Prevent this by adding a user namespace pointer to the fown_struct, and
>>> enforcing that a process causing a signal to be sent be in the same
>>> user namespace as the file owner.
>> This patch breaks the X server (stock FC5 install) with CONFIG_USER_NS=n.
>> Neither the USB mouse nor the trackpad work.  They work OK under GPM.
>>
>> Setting CONFIG_USER_NS=y "fixes" this.  This bug was not observed in
>> 2.6.20-rc3-mm1 because that kernel had user-ns-always-on.patch for other
>> reasons.  (I'll restore that patch).
>>
>> There's nothing very interesting here:
>
[ ... ]
> 
> I can't see any reason for this in the code or comparative ltp runs.
> Cedric is testing on a fc6 laptop, hopefully he can reproduce it.

I did reproduce it on a FC5 desktop finally. 

get_user_ns() returns NULL when CONFIG_USER_NS=n and this breaks  
sigio_perm() which does not expect NULL values for ->user_ns.

I would fix this with the following patch.

C.


Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>

---
 include/linux/user_namespace.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: 2.6.20-rc4-mm1/include/linux/user_namespace.h
===================================================================
--- 2.6.20-rc4-mm1.orig/include/linux/user_namespace.h
+++ 2.6.20-rc4-mm1/include/linux/user_namespace.h
@@ -49,7 +49,7 @@

 static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
 {
-	return NULL;
+	return &init_user_ns;
 }

 static inline int unshare_user_ns(unsigned long flags,

  reply	other threads:[~2007-01-15 15:03 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-04 18:06 [PATCH -mm 0/8] user ns: Introduction Serge E. Hallyn
2007-01-04 18:10 ` [PATCH -mm 1/8] nsproxy: externalizes exit_task_namespaces Serge E. Hallyn
2007-01-04 18:11 ` [PATCH -mm 2/8] user namespace: add the framework Serge E. Hallyn
2007-01-04 21:16   ` Serge E. Hallyn
2007-01-04 18:11 ` [PATCH -mm 3/8] user ns: add user_namespace ptr to vfsmount Serge E. Hallyn
2007-01-04 18:11 ` [PATCH -mm 4/8] user ns: hook permission Serge E. Hallyn
2007-01-04 18:12 ` [PATCH -mm 5/8] user ns: prepare copy_tree, copy_mnt, and their callers to handle errs Serge E. Hallyn
2007-01-04 19:00   ` Frederik Deweerdt
2007-01-04 19:35     ` Serge E. Hallyn
2007-01-04 18:12 ` [PATCH -mm 6/8] user ns: implement shared mounts Serge E. Hallyn
2007-01-04 18:12 ` [PATCH -mm 7/8] user_ns: handle file sigio Serge E. Hallyn
2007-01-12  5:20   ` Andrew Morton
2007-01-15  7:26     ` Serge E. Hallyn
2007-01-15 15:03       ` Cedric Le Goater [this message]
2007-01-15 15:28         ` Serge E. Hallyn
2007-01-15 17:35           ` Cedric Le Goater
2007-01-16 11:04             ` [PATCH -mm] user_ns: remove CONFIG_USER_NS Cedric Le Goater
2007-01-16 14:53               ` Serge E. Hallyn
2007-01-04 18:13 ` [PATCH -mm 8/8] user ns: implement user ns unshare Serge E. Hallyn
2007-01-04 19:07   ` Frederik Deweerdt
2007-01-04 19:43     ` Serge E. Hallyn
2007-01-04 22:03       ` Andrew Morton
2007-01-04 22:07         ` Andrew Morton
2007-01-04 22:23     ` Valdis.Kletnieks
2007-01-04 22:52       ` Serge E. Hallyn
2007-01-05  2:02         ` Valdis.Kletnieks
2007-01-05  4:35           ` Serge E. Hallyn
2007-01-05  4:03 ` [PATCH -mm 0/8] user ns: Introduction Andrew Morton
2007-01-05  5:43   ` Serge E. Hallyn
2007-01-05  7:00     ` Serge E. Hallyn

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