Subject: [PATCH] NFS: Fix infinite loop in gss_create_upcall()

From: Bryan Schumaker <[email-masked]>
Date: Tue, 12 Apr 2011 13:41:04 -0400

On 04/11/2011 05:08 PM, Jiri Slaby wrote:
> 
> Sorry for an extra message. I've just found out that there appears
> messages in dmesg:
> [   58.656048] RPC: AUTH_GSS upcall timed out.
> [   58.656050] Please check user daemon is running.
> [   88.656065] RPC: AUTH_GSS upcall timed out.
> [   88.656068] Please check user daemon is running.
> [  118.656077] RPC: AUTH_GSS upcall timed out.
> [  118.656080] Please check user daemon is running.
> [  148.656049] RPC: AUTH_GSS upcall timed out.
> [  148.656052] Please check user daemon is running.
> [  178.656046] RPC: AUTH_GSS upcall timed out.
> [  178.656049] Please check user daemon is running.
> 
> 
> I instrumented the code and it's stuck with trying RPC_AUTH_GSS_KRB5.
> 
> I don't use GSS at all.
> 
> regards,

Does this patch help?

- Bryan

There can be an infinite loop if gss_create_upcall() is called without
the userspace program running.  To prevent this, we return -EACCES if
we notice that pipe_version hasn't changed (indicating that the pipe
has not been opened).

Signed-off-by: Bryan Schumaker <[email-masked]>
--
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 9bf41ea..8a03ee0 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2224,8 +2224,9 @@ static int nfs4_proc_get_root(struct nfs_server *server, struct nfs_fh *fhandle,
 
 	for (i = 0; i < len; i++) {
 		status = nfs4_lookup_root_sec(server, fhandle, info, flav_array[i]);
-		if (status != -EPERM)
-			break;
+		if (status == -EPERM || status == -EACCES)
+			continue;
+		break;
 	}
 	if (status == 0)
 		status = nfs4_server_capabilities(server, fhandle);
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index f3914d0..339ba64 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -520,7 +520,7 @@ gss_refresh_upcall(struct rpc_task *task)
 		warn_gssd();
 		task->tk_timeout = 15*HZ;
 		rpc_sleep_on(&pipe_version_rpc_waitqueue, task, NULL);
-		return 0;
+		return -EAGAIN;
 	}
 	if (IS_ERR(gss_msg)) {
 		err = PTR_ERR(gss_msg);
@@ -563,10 +563,12 @@ retry:
 	if (PTR_ERR(gss_msg) == -EAGAIN) {
 		err = wait_event_interruptible_timeout(pipe_version_waitqueue,
 				pipe_version >= 0, 15*HZ);
+		if (pipe_version < 0) {
+			warn_gssd();
+			err = -EACCES;
+		}
 		if (err)
 			goto out;
-		if (pipe_version < 0)
-			warn_gssd();
 		goto retry;
 	}
 	if (IS_ERR(gss_msg)) {

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