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SUNRPC: Fix a race in rpc_info_open 

There is a race between rpc_info_open and rpc_release_client()
in that nothing stops a process from opening the file after
the clnt->cl_kref goes to zero.

Fix this by using atomic_inc_unless_zero()...

Reported-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
This commit is contained in:
Trond Myklebust 2010-09-12 19:55:25 -04:00
parent 5a67657a2e
commit 006abe887c
3 changed files with 21 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/sunrpc/clnt.h
View File

@ -30,7 +30,7 @@ struct rpc_inode;
* The high-level client handle
*/
struct rpc_clnt {
struct kref cl_kref; /* Number of references */
atomic_t cl_count; /* Number of references */
struct list_head cl_clients; /* Global list of clients */
struct list_head cl_tasks; /* List of tasks */
spinlock_t cl_lock; /* spinlock */

26
net/sunrpc/clnt.c
View File

@ -226,7 +226,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
goto out_no_principal;
}
kref_init(&clnt->cl_kref);
atomic_set(&clnt->cl_count, 1);
err = rpc_setup_pipedir(clnt, program->pipe_dir_name);
if (err < 0)
@ -390,14 +390,14 @@ rpc_clone_client(struct rpc_clnt *clnt)
if (new->cl_principal == NULL)
goto out_no_principal;
}
kref_init(&new->cl_kref);
atomic_set(&new->cl_count, 1);
err = rpc_setup_pipedir(new, clnt->cl_program->pipe_dir_name);
if (err != 0)
goto out_no_path;
if (new->cl_auth)
atomic_inc(&new->cl_auth->au_count);
xprt_get(clnt->cl_xprt);
kref_get(&clnt->cl_kref);
atomic_inc(&clnt->cl_count);
rpc_register_client(new);
rpciod_up();
return new;
@ -465,10 +465,8 @@ EXPORT_SYMBOL_GPL(rpc_shutdown_client);
* Free an RPC client
*/
static void
rpc_free_client(struct kref *kref)
rpc_free_client(struct rpc_clnt *clnt)
{
struct rpc_clnt *clnt = container_of(kref, struct rpc_clnt, cl_kref);
dprintk("RPC: destroying %s client for %s\n",
clnt->cl_protname, clnt->cl_server);
if (!IS_ERR(clnt->cl_path.dentry)) {
@ -495,12 +493,10 @@ rpc_free_client(struct kref *kref)
* Free an RPC client
*/
static void
rpc_free_auth(struct kref *kref)
rpc_free_auth(struct rpc_clnt *clnt)
{
struct rpc_clnt *clnt = container_of(kref, struct rpc_clnt, cl_kref);
if (clnt->cl_auth == NULL) {
rpc_free_client(kref);
rpc_free_client(clnt);
return;
}
@ -509,10 +505,11 @@ rpc_free_auth(struct kref *kref)
* release remaining GSS contexts. This mechanism ensures
* that it can do so safely.
*/
kref_init(kref);
atomic_inc(&clnt->cl_count);
rpcauth_release(clnt->cl_auth);
clnt->cl_auth = NULL;
kref_put(kref, rpc_free_client);
if (atomic_dec_and_test(&clnt->cl_count))
rpc_free_client(clnt);
}
/*
@ -525,7 +522,8 @@ rpc_release_client(struct rpc_clnt *clnt)
if (list_empty(&clnt->cl_tasks))
wake_up(&destroy_wait);
kref_put(&clnt->cl_kref, rpc_free_auth);
if (atomic_dec_and_test(&clnt->cl_count))
rpc_free_auth(clnt);
}
/**
@ -588,7 +586,7 @@ void rpc_task_set_client(struct rpc_task *task, struct rpc_clnt *clnt)
if (clnt != NULL) {
rpc_task_release_client(task);
task->tk_client = clnt;
kref_get(&clnt->cl_kref);
atomic_inc(&clnt->cl_count);
if (clnt->cl_softrtry)
task->tk_flags |= RPC_TASK_SOFT;
/* Add to the client's list of all tasks */

14
net/sunrpc/rpc_pipe.c
View File

@ -371,21 +371,23 @@ rpc_show_info(struct seq_file *m, void *v)
static int
rpc_info_open(struct inode *inode, struct file *file)
{
struct rpc_clnt *clnt;
struct rpc_clnt *clnt = NULL;
int ret = single_open(file, rpc_show_info, NULL);
if (!ret) {
struct seq_file *m = file->private_data;
mutex_lock(&inode->i_mutex);
clnt = RPC_I(inode)->private;
if (clnt) {
kref_get(&clnt->cl_kref);
spin_lock(&file->f_path.dentry->d_lock);
if (!d_unhashed(file->f_path.dentry))
clnt = RPC_I(inode)->private;
if (clnt != NULL && atomic_inc_not_zero(&clnt->cl_count)) {
spin_unlock(&file->f_path.dentry->d_lock);
m->private = clnt;
} else {
spin_unlock(&file->f_path.dentry->d_lock);
single_release(inode, file);
ret = -EINVAL;
}
mutex_unlock(&inode->i_mutex);
}
return ret;
}