[PATCH] net: qrtr: ns: Fix the incorrect usage of rcu_read_lock()

[Manivannan Sadhasivam]

The rcu_read_lock() is not supposed to lock the kernel_sendmsg() API
since it has the lock_sock() in qrtr_sendmsg() which will sleep. Hence,
fix it by excluding the locking for kernel_sendmsg().

Fixes: a7809ff90ce6 ("net: qrtr: ns: Protect radix_tree_deref_slot() using rcu 
read locks")
Reported-by: Doug Anderson <diand...@chromium.org>
Tested-by: Alex Elder <el...@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasi...@linaro.org>
---
 net/qrtr/ns.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/net/qrtr/ns.c b/net/qrtr/ns.c
index 934999b56d60..0515433de922 100644
--- a/net/qrtr/ns.c
+++ b/net/qrtr/ns.c
@@ -203,15 +203,17 @@ static int announce_servers(struct sockaddr_qrtr *sq)
        /* Announce the list of servers registered in this node */
        radix_tree_for_each_slot(slot, &node->servers, &iter, 0) {
                srv = radix_tree_deref_slot(slot);
+               rcu_read_unlock();
 
                ret = service_announce_new(sq, srv);
                if (ret < 0) {
                        pr_err("failed to announce new service\n");
-                       goto err_out;
+                       return ret;
                }
+
+               rcu_read_lock();
        }
 
-err_out:
        rcu_read_unlock();
 
        return ret;
@@ -352,7 +354,9 @@ static int ctrl_cmd_bye(struct sockaddr_qrtr *from)
        /* Advertise removal of this client to all servers of remote node */
        radix_tree_for_each_slot(slot, &node->servers, &iter, 0) {
                srv = radix_tree_deref_slot(slot);
+               rcu_read_unlock();
                server_del(node, srv->port);
+               rcu_read_lock();
        }
        rcu_read_unlock();
 
@@ -368,6 +372,7 @@ static int ctrl_cmd_bye(struct sockaddr_qrtr *from)
        rcu_read_lock();
        radix_tree_for_each_slot(slot, &local_node->servers, &iter, 0) {
                srv = radix_tree_deref_slot(slot);
+               rcu_read_unlock();
 
                sq.sq_family = AF_QIPCRTR;
                sq.sq_node = srv->node;
@@ -379,11 +384,11 @@ static int ctrl_cmd_bye(struct sockaddr_qrtr *from)
                ret = kernel_sendmsg(qrtr_ns.sock, &msg, &iv, 1, sizeof(pkt));
                if (ret < 0) {
                        pr_err("failed to send bye cmd\n");
-                       goto err_out;
+                       return ret;
                }
+               rcu_read_lock();
        }
 
-err_out:
        rcu_read_unlock();
 
        return ret;
@@ -447,6 +452,7 @@ static int ctrl_cmd_del_client(struct sockaddr_qrtr *from,
        rcu_read_lock();
        radix_tree_for_each_slot(slot, &local_node->servers, &iter, 0) {
                srv = radix_tree_deref_slot(slot);
+               rcu_read_unlock();
 
                sq.sq_family = AF_QIPCRTR;
                sq.sq_node = srv->node;
@@ -458,11 +464,11 @@ static int ctrl_cmd_del_client(struct sockaddr_qrtr *from,
                ret = kernel_sendmsg(qrtr_ns.sock, &msg, &iv, 1, sizeof(pkt));
                if (ret < 0) {
                        pr_err("failed to send del client cmd\n");
-                       goto err_out;
+                       return ret;
                }
+               rcu_read_lock();
        }
 
-err_out:
        rcu_read_unlock();
 
        return ret;
@@ -580,7 +586,9 @@ static int ctrl_cmd_new_lookup(struct sockaddr_qrtr *from,
                        if (!server_match(srv, &filter))
                                continue;
 
+                       rcu_read_unlock();
                        lookup_notify(from, srv, true);
+                       rcu_read_lock();
                }
        }
        rcu_read_unlock();
-- 
2.17.1