| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.12 097/116] SUNRPC: Avoid deep recursion in rpc_release_client | Date | Tue, 26 Nov 2013 16:57:50 -0800 |
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3.12-stable review patch. If anyone has any objections, please let me know.
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From: Trond Myklebust <Trond.Myklebust@netapp.com>
commit d07ba8422f1e58be94cc98a1f475946dc1b89f1b upstream.
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: Jeff Layton <jlayton@redhat.com> Reported-by: Weston Andros Adamson <dros@netapp.com> Reported-by: Bruce Fields <bfields@fieldses.org> Link: http://lkml.kernel.org/r/2C73011F-0939-434C-9E4D-13A1EB1403D7@netapp.com Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- net/sunrpc/clnt.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-)
--- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -656,14 +656,16 @@ 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); @@ -672,18 +674,17 @@ 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 @@ -694,7 +695,8 @@ 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; } /* @@ -705,10 +707,13 @@ rpc_release_client(struct rpc_clnt *clnt { dprintk("RPC: rpc_release_client(%p)\n", clnt); - if (list_empty(&clnt->cl_tasks)) - wake_up(&destroy_wait); - if (atomic_dec_and_test(&clnt->cl_count)) - rpc_free_auth(clnt); + do { + if (list_empty(&clnt->cl_tasks)) + wake_up(&destroy_wait); + 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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