Commit d07ba842 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

SUNRPC: Avoid deep recursion in rpc_release_client 



In cases where an rpc client has a parent hierarchy, then
rpc_free_client may end up calling rpc_release_client() on the
parent, thus recursing back into rpc_free_client. If the hierarchy
is deep enough, then we can get into situations where the stack
simply overflows.

The fix is to have rpc_release_client() loop so that it can take
care of the parent rpc client hierarchy without needing to
recurse.

Reported-by: default avatarJeff Layton <jlayton@redhat.com>
Reported-by: default avatarWeston Andros Adamson <dros@netapp.com>
Reported-by: default avatarBruce Fields <bfields@fieldses.org>
Link: http://lkml.kernel.org/r/2C73011F-0939-434C-9E4D-13A1EB1403D7@netapp.com


Cc: stable@vger.kernel.org
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent a6b31d18

net/sunrpc/clnt.c

+17 −12
Original line number Diff line number Diff line
@@ -750,14 +750,16 @@ EXPORT_SYMBOL_GPL(rpc_shutdown_client); 
/*

 * Free an RPC client

 */

static void

static struct rpc_clnt *

rpc_free_client(struct rpc_clnt *clnt)

{

	struct rpc_clnt *parent = NULL;



	dprintk_rcu("RPC:       destroying %s client for %s\n",

			clnt->cl_program->name,

			rcu_dereference(clnt->cl_xprt)->servername);

	if (clnt->cl_parent != clnt)

		rpc_release_client(clnt->cl_parent);

		parent = clnt->cl_parent;

	rpc_clnt_remove_pipedir(clnt);

	rpc_unregister_client(clnt);

	rpc_free_iostats(clnt->cl_metrics);
@@ -766,18 +768,17 @@ rpc_free_client(struct rpc_clnt *clnt) 
	rpciod_down();

	rpc_free_clid(clnt);

	kfree(clnt);

	return parent;

}



/*

 * Free an RPC client

 */

static void

static struct rpc_clnt * 

rpc_free_auth(struct rpc_clnt *clnt)

{

	if (clnt->cl_auth == NULL) {

		rpc_free_client(clnt);

		return;

	}

	if (clnt->cl_auth == NULL)

		return rpc_free_client(clnt);



	/*

	 * Note: RPCSEC_GSS may need to send NULL RPC calls in order to
@@ -788,7 +789,8 @@ rpc_free_auth(struct rpc_clnt *clnt) 
	rpcauth_release(clnt->cl_auth);

	clnt->cl_auth = NULL;

	if (atomic_dec_and_test(&clnt->cl_count))

		rpc_free_client(clnt);

		return rpc_free_client(clnt);

	return NULL;

}



/*
@@ -799,10 +801,13 @@ rpc_release_client(struct rpc_clnt *clnt) 
{

	dprintk("RPC:       rpc_release_client(%p)\n", clnt);



	do {

		if (list_empty(&clnt->cl_tasks))

			wake_up(&destroy_wait);

	if (atomic_dec_and_test(&clnt->cl_count))

		rpc_free_auth(clnt);

		if (!atomic_dec_and_test(&clnt->cl_count))

			break;

		clnt = rpc_free_auth(clnt);

	} while (clnt != NULL);

}

EXPORT_SYMBOL_GPL(rpc_release_client);

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