linux-kernel - [PATCH V1 3/4] net: qrtr: Change port allocation to use cyclic idr

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Date:   Sun, 30 Aug 2020 20:08:11 +0530
From:   Deepak Kumar Singh <deesin@...eaurora.org>
To:     bjorn.andersson@...aro.org, clew@...eaurora.org
Cc:     mathieu.poirier@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Carl Huang <cjhuang@...eaurora.org>,
        Necip Fazil Yildiran <necip@...gle.com>,
        netdev@...r.kernel.org (open list:NETWORKING [GENERAL])
Subject: [PATCH V1 3/4] net: qrtr: Change port allocation to use cyclic idr

From: Chris Lew <clew@...eaurora.org>

There is a race for clients that open sockets before the control port
is bound. If a client gets an idr that was allocated before the control
port is bound, there is a chance the previous address owner sent lookup
packets to the control port. The new address owner will get residual
responses to this the lookup packets.

Change the idr_alloc to idr_alloc_cyclic so new idr's are allocated
instead of trying to reuse the freed idrs.
---
 net/qrtr/qrtr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
index 4496b75..e2dd38e 100644
--- a/net/qrtr/qrtr.c
+++ b/net/qrtr/qrtr.c
@@ -744,7 +744,8 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port)
 	mutex_lock(&qrtr_port_lock);
 	if (!*port) {
 		min_port = QRTR_MIN_EPH_SOCKET;
-		rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, QRTR_MAX_EPH_SOCKET, GFP_ATOMIC);
+		rc = idr_alloc_cyclic(&qrtr_ports, ipc, &min_port,
+				      QRTR_MAX_EPH_SOCKET, GFP_ATOMIC);
 		if (!rc)
 			*port = min_port;
 	} else if (*port < QRTR_MIN_EPH_SOCKET && !capable(CAP_NET_ADMIN)) {
@@ -754,7 +755,8 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port)
 		rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, 0, GFP_ATOMIC);
 	} else {
 		min_port = *port;
-		rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, *port, GFP_ATOMIC);
+		rc = idr_alloc_cyclic(&qrtr_ports, ipc, &min_port,
+				      *port, GFP_ATOMIC);
 		if (!rc)
 			*port = min_port;
 	}
-- 
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