From 384816051ca9125cd54750e59c780c2a2655fa4f Mon Sep 17 00:00:00 2001 From: Stanislav Kinsbursky Date: Mon, 24 Jun 2013 11:52:38 +0400 Subject: [PATCH] SUNRPC: fix races on PipeFS MOUNT notifications Below are races, when RPC client can be created without PiepFS dentries CPU#0 CPU#1 ----------------------------- ----------------------------- rpc_new_client rpc_fill_super rpc_setup_pipedir mutex_lock(&sn->pipefs_sb_lock) rpc_get_sb_net == NULL (no per-net PipeFS superblock) sn->pipefs_sb = sb; notifier_call_chain(MOUNT) (client is not in the list) rpc_register_client (client without pipes dentries) To fix this patch: 1) makes PipeFS mount notification call with pipefs_sb_lock being held. 2) releases pipefs_sb_lock on new SUNRPC client creation only after registration. Signed-off-by: Stanislav Kinsbursky Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust --- net/sunrpc/clnt.c | 26 +++++++++++++++----------- net/sunrpc/rpc_pipe.c | 3 +++ 2 files changed, 18 insertions(+), 11 deletions(-) diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index 5a750b9c3640..b827a4b91975 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -157,20 +157,15 @@ static struct dentry *rpc_setup_pipedir_sb(struct super_block *sb, } static int -rpc_setup_pipedir(struct rpc_clnt *clnt, const char *dir_name) +rpc_setup_pipedir(struct rpc_clnt *clnt, const char *dir_name, + struct super_block *pipefs_sb) { - struct net *net = rpc_net_ns(clnt); - struct super_block *pipefs_sb; struct dentry *dentry; clnt->cl_dentry = NULL; if (dir_name == NULL) return 0; - pipefs_sb = rpc_get_sb_net(net); - if (!pipefs_sb) - return 0; dentry = rpc_setup_pipedir_sb(pipefs_sb, clnt, dir_name); - rpc_put_sb_net(net); if (IS_ERR(dentry)) return PTR_ERR(dentry); clnt->cl_dentry = dentry; @@ -296,6 +291,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru struct rpc_clnt *clnt = NULL; struct rpc_auth *auth; int err; + struct super_block *pipefs_sb; /* sanity check the name before trying to print it */ dprintk("RPC: creating %s client for %s (xprt %p)\n", @@ -354,9 +350,12 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru atomic_set(&clnt->cl_count, 1); - err = rpc_setup_pipedir(clnt, program->pipe_dir_name); - if (err < 0) - goto out_no_path; + pipefs_sb = rpc_get_sb_net(rpc_net_ns(clnt)); + if (pipefs_sb) { + err = rpc_setup_pipedir(clnt, program->pipe_dir_name, pipefs_sb); + if (err) + goto out_no_path; + } auth = rpcauth_create(args->authflavor, clnt); if (IS_ERR(auth)) { @@ -369,11 +368,16 @@ 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_register_client(clnt); + if (pipefs_sb) + rpc_put_sb_net(rpc_net_ns(clnt)); return clnt; out_no_auth: - rpc_clnt_remove_pipedir(clnt); + if (pipefs_sb) + __rpc_clnt_remove_pipedir(clnt); out_no_path: + if (pipefs_sb) + rpc_put_sb_net(rpc_net_ns(clnt)); kfree(clnt->cl_principal); out_no_principal: rpc_free_iostats(clnt->cl_metrics); diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c index a816b3a69059..e02823bdfe98 100644 --- a/net/sunrpc/rpc_pipe.c +++ b/net/sunrpc/rpc_pipe.c @@ -1127,6 +1127,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent) return -ENOMEM; dprintk("RPC: sending pipefs MOUNT notification for net %p%s\n", net, NET_NAME(net)); + mutex_lock(&sn->pipefs_sb_lock); sn->pipefs_sb = sb; err = blocking_notifier_call_chain(&rpc_pipefs_notifier_list, RPC_PIPEFS_MOUNT, @@ -1134,6 +1135,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent) if (err) goto err_depopulate; sb->s_fs_info = get_net(net); + mutex_unlock(&sn->pipefs_sb_lock); return 0; err_depopulate: @@ -1142,6 +1144,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent) sb); sn->pipefs_sb = NULL; __rpc_depopulate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF); + mutex_unlock(&sn->pipefs_sb_lock); return err; }