linux-kernel - [PATCH] net: qrtr: ns: Fix the incorrect usage of rcu_read

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Message-Id: <20201002141531.7081-1-manivannan.sadhasivam@linaro.org>
Date:   Fri,  2 Oct 2020 19:45:31 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     bjorn.andersson@...aro.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, dianders@...omium.org,
        elder@...aro.org,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH] net: qrtr: ns: Fix the incorrect usage of rcu_read_lock()

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 <dianders@...omium.org>
Tested-by: Alex Elder <elder@...aro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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