Re: [PATCH v2] SUNRPC: check current nsproxy before set of node nameon client creation
From: Stanislav Kinsbursky
Date: Sat Sep 08 2012 - 02:01:02 EST
08.09.2012 01:32, Myklebust, Trond ÐÐÑÐÑ:
On Mon, 2012-08-13 at 08:10 -0400, Jeff Layton wrote:
On Mon, 13 Aug 2012 15:37:31 +0400
Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx> wrote:
v2:
1) rpc_clnt_set_nodename() prototype updated.
2) fixed errors in comment.
When child reaper exits, it can destroy mount namespace it belongs to, and if
there are NFS mounts inside, then it will try to umount them. But in this
point current->nsproxy is set to NULL and all namespaces will be destroyed one
by one. I.e. we can't dereference current->nsproxy to obtain uts namespace.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
---
net/sunrpc/clnt.c | 16 +++++++++++++---
1 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 9a9676e..8fbcbc8 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -277,8 +277,18 @@ void rpc_clients_notifier_unregister(void)
return rpc_pipefs_notifier_unregister(&rpc_clients_block);
}
-static void rpc_clnt_set_nodename(struct rpc_clnt *clnt, const char *nodename)
+static void rpc_clnt_set_nodename(struct rpc_clnt *clnt)
{
+ const char *nodename;
+
+ /*
+ * We have to protect against dying child reaper, which has released
+ * its nsproxy already and is trying to destroy mount namespace.
+ */
+ if (current->nsproxy == NULL)
+ return;
+
+ nodename = utsname()->nodename;
clnt->cl_nodelen = strlen(nodename);
if (clnt->cl_nodelen > UNX_MAXNODENAME)
clnt->cl_nodelen = UNX_MAXNODENAME;
@@ -365,7 +375,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
}
/* save the nodename */
- rpc_clnt_set_nodename(clnt, utsname()->nodename);
+ rpc_clnt_set_nodename(clnt);
rpc_register_client(clnt);
return clnt;
@@ -524,7 +534,7 @@ rpc_clone_client(struct rpc_clnt *clnt)
err = rpc_setup_pipedir(new, clnt->cl_program->pipe_dir_name);
if (err != 0)
goto out_no_path;
- rpc_clnt_set_nodename(new, utsname()->nodename);
+ rpc_clnt_set_nodename(new);
if (new->cl_auth)
atomic_inc(&new->cl_auth->au_count);
atomic_inc(&clnt->cl_count);
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Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
OK, colour me confused (again).
What color?
Why should a umount trigger an
rpc_create() or rpc_clone_client()?
It calls nsm_create().
Here is the trace (https://bugzilla.redhat.com/show_bug.cgi?id=830862,
comment 68):
CR2: 0000000000000008
Process mysqld
Call Trace:
? __schedule+0x3c7
nsm_create+0x8b
nsm_mon_unmon+0x64
nlm_destroy_host_locked+0x6b
nlmclnt_release_host+0x88
nlmclnt_done+0x1a
nfs_destroy_server+0x24
nfs_free_server+0xce
nfs_kill_super+0x34
deactivate_locked_super+0x57
deactivate_super+0x4e
mntput_no_expire+0xcc
mntput+0x26
release_mounts+0x77
put_mnt_ns+0x78
free_nsproxy+0x1f
switch_task_namespaces+0x50
exit_task_namespaces+0x10
do_exit+0x456
do_group_exit+0x3f
sys_exit_group+0x17
system_call_fastpath+0x16
RIP rpc_create+0x401 [sunrpc]
Kernel panic - not syncing
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