===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
linux/nfs-2.6/fs/nfs/client.c:1289 invoked rcu_dereference_check() without protection!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
no locks held by mount.nfs/2525.
stack backtrace:
Pid: 2525, comm: mount.nfs Not tainted 2.6.39-rc3-00045-g2fb8dcc #6
Call Trace:
[<ffffffff8107c44b>] lockdep_rcu_dereference+0xaa/0xb2
[<ffffffffa033ed38>] nfs4_init_client+0x126/0x1d7 [nfs]
[<ffffffffa033f924>] nfs_get_client+0x459/0x5b1 [nfs]
[<ffffffff81085735>] ? is_module_address+0xe/0x16
[<ffffffff8107bee5>] ? lockdep_init_map+0x9b/0x110
[<ffffffffa033fb02>] nfs4_set_client+0x86/0xda [nfs]
[<ffffffffa034037e>] nfs4_create_server+0xf7/0x228 [nfs]
[<ffffffff811148cb>] ? kmem_cache_alloc_trace+0xaf/0xbe
[<ffffffffa034922b>] nfs4_remote_mount+0x80/0x1ec [nfs]
[<ffffffff81123e3c>] mount_fs+0x70/0x157
[<ffffffff810f251a>] ? __alloc_percpu+0x10/0x12
[<ffffffff8113a83a>] vfs_kern_mount+0x65/0xa0
[<ffffffffa0349603>] nfs_do_root_mount+0x7b/0x9a [nfs]
[<ffffffffa034997f>] nfs4_try_mount+0x5a/0xbf [nfs]
[<ffffffffa034ac0c>] nfs_fs_mount+0x4a6/0x6fe [nfs]
[<ffffffff81123e3c>] mount_fs+0x70/0x157
[<ffffffff810f251a>] ? __alloc_percpu+0x10/0x12
[<ffffffff8113a83a>] vfs_kern_mount+0x65/0xa0
[<ffffffff8113b1eb>] do_kern_mount+0x4d/0xdd
[<ffffffff8113c026>] do_mount+0x6bd/0x720
[<ffffffff8113c111>] sys_mount+0x88/0xc2
[<ffffffff814970c2>] system_call_fastpath+0x16/0x1b
Commit cf8bebc9 "SUNRPC: Use RCU to dereference the rpc_client cl_xprt
structure" seems to have introduced this.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
fs/nfs/client.c | 40 +++++++++++++++++++++++-----------------
net/sunrpc/xprt.c | 2 ++
2 files changed, 25 insertions(+), 17 deletions(-)
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 86cc751..8f8035e 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1270,29 +1270,35 @@ nfs4_find_client_sessionid(const struct sockaddr *addr,
*/
static int nfs4_init_callback(struct nfs_client *clp)
{
+ struct rpc_xprt *xprt;
int error;
- if (clp->rpc_ops->version == 4) {
- struct rpc_xprt *xprt;
+ if (clp->rpc_ops->version != 4)
+ return 0;
- xprt = rcu_dereference(clp->cl_rpcclient->cl_xprt);
+ rcu_read_lock();
+ xprt = xprt_get(rcu_dereference(clp->cl_rpcclient->cl_xprt));
+ rcu_read_unlock();
- if (nfs4_has_session(clp)) {
- error = xprt_setup_backchannel(xprt,
- NFS41_BC_MIN_CALLBACKS);
- if (error < 0)
- return error;
- }
+ if (nfs4_has_session(clp)) {
+ error = xprt_setup_backchannel(xprt, NFS41_BC_MIN_CALLBACKS);
+ if (error < 0)
+ goto out;
+ }
- error = nfs_callback_up(clp->cl_mvops->minor_version, xprt);
- if (error < 0) {
- dprintk("%s: failed to start callback. Error = %d\n",
- __func__, error);
- return error;
- }
- __set_bit(NFS_CS_CALLBACK, &clp->cl_res_state);
+ error = nfs_callback_up(clp->cl_mvops->minor_version, xprt);
+ if (error < 0) {
+ dprintk("%s: failed to start callback. Error = %d\n",
+ __func__, error);
+ goto out;
}
- return 0;
+
+ error = 0;
+ __set_bit(NFS_CS_CALLBACK, &clp->cl_res_state);
+
+out:
+ xprt_put(xprt);
+ return error;
}
/*
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 201debb..531ab6b 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1187,6 +1187,7 @@ void xprt_put(struct rpc_xprt *xprt)
if (atomic_dec_and_test(&xprt->count))
xprt_destroy(xprt);
}
+EXPORT_SYMBOL_GPL(xprt_put);
/**
* xprt_get - return a reference to an RPC transport.
@@ -1199,3 +1200,4 @@ struct rpc_xprt *xprt_get(struct rpc_xprt *xprt)
return xprt;
return NULL;
}
+EXPORT_SYMBOL_GPL(xprt_get);
--
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