Date: Fri, 20 Apr 2012 11:23:57 +0400 From: Pavel Emelyanov <xemul@...allels.com> To: "Eric W. Biederman" <ebiederm@...ssion.com> CC: Eugene Teo <eugeneteo@...nel.sg>, Marcus Meissner <meissner@...e.de>, OSS Security List <oss-security@...ts.openwall.com>, "security@...nel.org" <security@...nel.org>, Sukadev Bhattiprolu <sukadev@...ibm.com>, Serge Hallyn <serge.hallyn@...onical.com> Subject: Re: CVE request: pid namespace leak in kernel 3.0 and 3.1 On 04/20/2012 11:20 AM, Eric W. Biederman wrote: > Pavel Emelyanov <xemul@...allels.com> writes: > >> On 04/20/2012 07:10 AM, Eugene Teo wrote: >>>> So we know what is holding the pid namespace reference. >>>> >>>> Additional thoughts. >>>> >>>> Does echo 3 > /proc/sys/vm/drop_caches clear up the issue? >>> >>> No. >>> >>>> Is there a corresponding task_struct leak? >>> >>> Yes. >>> >>>> I don't have much of a clue or much concern as this seems fixed in later kernels but I am happy to suggest things to look for to help narrow this down. >>> >>> I'm helping to provide more information. >> >> Is there also a vfsmount struct leak as well? The pidns creating implies >> kern-mount-ing of a proc and it should be released when child reaper of >> the namespace dies. > > In this case the user is vsftp which is an entertaining user. > > Roughly for every connection vsftp does: > - accepts the connection > - forks a server process > - unshares the network ipc and pid namespaces for additional isolation > - drops privilegs? > - serves up the file. > > Since vsftp does not want any of the features of namespaces it does not > setup mounts or any of that. I'm talking about the call to pid_ns_prepare_proc which does kern_mount thus bringing the proc sb in memory and pinning the init's pid on it. > vsftp simply wants a way to reduce the > the chance that a bug in the implemenation of vsftp will all the server > to be compromised. > > To that extent I believe the reproduce program was very representative > of what vsftp is doing. > > Eric > . >
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