linux-kernel - Re: [RFC][PATCH] sunrpc: fix oops in rpc_create() when the mount namespace is unshared

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Date:	Tue, 09 Sep 2008 13:54:39 +0200
From:	Cedric Le Goater <clg@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Trond Myklebust <trond.myklebust@....uio.no>,
	Chuck Lever <chuck.lever@...cle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Containers <containers@...ts.osdl.org>,
	linux-nfs@...r.kernel.org
Subject: Re: [RFC][PATCH] sunrpc: fix oops in rpc_create() when the mount
 namespace is unshared

Eric W. Biederman wrote:
> Cedric Le Goater <clg@...ibm.com> writes:
> 
>> On a system with nfs mounts, if a task unshares its mount namespace,
>> a oops can occur when the system is rebooted if the task is the last
>> to unreference the nfs mount. It will try to create a rpc request
>> using utsname() which has been invalidated by free_nsproxy().
>>
>> The patch fixes the issue by using the global init_utsname() but at
>> the same time, it breaks the capability of identifying rpc clients
>> per uts namespace.
>>
>> Any better suggestions ?
> 
> Can we push utsname into rpc_create_args and push the access
> of utsname up the food chain?

struct rpc_create_args seems to be used only as a stack argument 
for rpc_create() it's not kept in any nfs or sunrpc objects.
 
> My gut feeling says we should capture the utsname or the
> uts_ns when we mount the nfs filesystem so we stay in sync
> for the life of the mount.

I see. It make sense but, looking at the code, the nfs and sunrpc 
will need some heavy changes ...

Thanks,

C.
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