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 <skinsbur...@parallels.com>
Cc: sta...@vger.kernel.org
---
net/sunrpc/clnt.c | 24 +++++++++++++-----------
net/sunrpc/rpc_pipe.c | 3 +++
2 files changed, 16 insertions(+), 11 deletions(-)
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 4bf2409..48888ee 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;
@@ -294,11 +289,16 @@ static int rpc_client_register(const struct
rpc_create_args *args,
{
const struct rpc_program *program = args->program;
struct rpc_auth *auth;
+ struct net *net = rpc_net_ns(clnt);
+ struct super_block *pipefs_sb;
int err = 0;
- err = rpc_setup_pipedir(clnt, program->pipe_dir_name);
- if (err < 0)
- goto out;
+ pipefs_sb = rpc_get_sb_net(net);
+ if (pipefs_sb) {
+ err = rpc_setup_pipedir(clnt, program->pipe_dir_name,
pipefs_sb);
+ if (err)
+ goto out;
+ }
auth = rpcauth_create(args->authflavor, clnt);
if (IS_ERR(auth)) {
@@ -310,10 +310,12 @@ static int rpc_client_register(const struct
rpc_create_args *args,
rpc_register_client(clnt);
out:
+ if (pipefs_sb)
+ rpc_put_sb_net(net);
return err;
err_auth:
- rpc_clnt_remove_pipedir(clnt);
+ __rpc_clnt_remove_pipedir(clnt);
goto out;
}
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index e7ce4b3..c512448 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -1126,6 +1126,7 @@ 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,
@@ -1133,6 +1134,7 @@ 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:
@@ -1141,6 +1143,7 @@ err_depopulate:
sb);
sn->pipefs_sb = NULL;
__rpc_depopulate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF);
+ mutex_unlock(&sn->pipefs_sb_lock);
return err;
}
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