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From: Wenbin Zeng <wenbin.zeng@gmail.com>
To: bfields@fieldses.org, davem@davemloft.net, viro@zeniv.linux.org.uk
Cc: jlayton@kernel.org, trond.myklebust@hammerspace.com,
	anna.schumaker@netapp.com, wenbinzeng@tencent.com,
	dsahern@gmail.com, nicolas.dichtel@6wind.com,
	willy@infradead.org, edumazet@google.com,
	jakub.kicinski@netronome.com, tyhicks@canonical.com,
	chuck.lever@oracle.com, neilb@suse.com,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, linux-nfs@vger.kernel.org
Subject: [PATCH v3 0/3] auth_gss: netns refcount leaks when use-gss-proxy==1
Date: Wed, 12 Jun 2019 20:09:27 +0800
Message-ID: <1560341370-24197-1-git-send-email-wenbinzeng@tencent.com> (raw)
In-Reply-To: <1556692945-3996-1-git-send-email-wenbinzeng@tencent.com>

This patch series fixes an auth_gss bug that results in netns refcount
leaks when use-gss-proxy is set to 1.

The problem was found in privileged docker containers with gssproxy service
enabled and /proc/net/rpc/use-gss-proxy set to 1, the corresponding
struct net->count ends up at 2 after container gets killed, the consequence
is that the struct net cannot be freed.

It turns out that write_gssp() called gssp_rpc_create() to create a rpc
client, this increases net->count by 2; rpcsec_gss_exit_net() is supposed
to decrease net->count but it never gets called because its call-path is:
        net->count==0 -> cleanup_net -> ops_exit_list -> rpcsec_gss_exit_net
Before rpcsec_gss_exit_net() gets called, net->count cannot reach 0, this
is a deadlock situation.

To fix the problem, we must break the deadlock, rpcsec_gss_exit_net()
should move out of the put() path and find another chance to get called,
I think nsfs_evict() is a good place to go, when netns inode gets evicted
we call rpcsec_gss_exit_net() to free the rpc client, this requires a new
callback i.e. evict to be added in struct proc_ns_operations, and add
netns_evict() as one of netns_operations as well.

v1->v2:
 * in nsfs_evict(), move ->evict() in front of ->put()
v2->v3:
 * rpcsec_gss_evict_net() directly call gss_svc_shutdown_net() regardless
   if gssp_clnt is null, this is exactly same to what rpcsec_gss_exit_net()
   previously did

Wenbin Zeng (3):
  nsfs: add evict callback into struct proc_ns_operations
  netns: add netns_evict into netns_operations
  auth_gss: fix deadlock that blocks rpcsec_gss_exit_net when
    use-gss-proxy==1

 fs/nsfs.c                      |  2 ++
 include/linux/proc_ns.h        |  1 +
 include/net/net_namespace.h    |  1 +
 net/core/net_namespace.c       | 12 ++++++++++++
 net/sunrpc/auth_gss/auth_gss.c |  4 ++--
 5 files changed, 18 insertions(+), 2 deletions(-)

-- 
1.8.3.1


  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-01  6:42 [PATCH " Wenbin Zeng
2019-05-01  6:42 ` [PATCH 1/3] nsfs: add evict callback into struct proc_ns_operations Wenbin Zeng
2019-05-02  3:04   ` Al Viro
2019-05-04 16:08     ` Wenbin Zeng
2019-05-01  6:42 ` [PATCH 2/3] netns: add netns_evict into netns_operations Wenbin Zeng
2019-05-04  4:10   ` David Miller
2019-05-01  6:42 ` [PATCH 3/3] auth_gss: fix deadlock that blocks rpcsec_gss_exit_net when use-gss-proxy==1 Wenbin Zeng
2019-05-09 20:52 ` [PATCH 0/3] auth_gss: netns refcount leaks " J. Bruce Fields
2019-05-10  5:09   ` Wenbin Zeng
2019-05-10  6:36 ` [PATCH v2 " Wenbin Zeng
2019-05-10  6:36   ` [PATCH v2 1/3] nsfs: add evict callback into struct proc_ns_operations Wenbin Zeng
2019-05-10  6:36   ` [PATCH v2 2/3] netns: add netns_evict into netns_operations Wenbin Zeng
2019-05-10 22:13     ` David Miller
2019-05-10  6:36   ` [PATCH v2 3/3] auth_gss: fix deadlock that blocks rpcsec_gss_exit_net when use-gss-proxy==1 Wenbin Zeng
2019-05-15  1:03   ` [PATCH v2 0/3] auth_gss: netns refcount leaks " J. Bruce Fields
2019-06-12  8:37     ` Wenbin Zeng
2019-06-12 15:52       ` J. Bruce Fields
2019-06-12 12:09 ` Wenbin Zeng [this message]
2019-06-12 12:09   ` [PATCH v3 1/3] nsfs: add evict callback into struct proc_ns_operations Wenbin Zeng
2019-06-12 12:09   ` [PATCH v3 2/3] netns: add netns_evict into netns_operations Wenbin Zeng
2019-06-12 12:09   ` [PATCH v3 3/3] auth_gss: fix deadlock that blocks rpcsec_gss_exit_net when use-gss-proxy==1 Wenbin Zeng
2019-08-01 19:53   ` [PATCH v3 0/3] auth_gss: netns refcount leaks " J. Bruce Fields

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