linux-kernel - [PATCH v2] net: qrtr: fix usage of idr in port assignment to socket

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Date:   Mon, 17 Aug 2020 07:39:01 +0000
From:   Necip Fazil Yildiran <fazilyildiran@...il.com>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     bjorn.andersson@...aro.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, dvyukov@...gle.com, elver@...gle.com,
        andreyknvl@...gle.com, glider@...gle.com, necip@...gle.com,
        syzbot+f31428628ef672716ea8@...kaller.appspotmail.com
Subject: [PATCH v2] net: qrtr: fix usage of idr in port assignment to socket

From: Necip Fazil Yildiran <necip@...gle.com>

Passing large uint32 sockaddr_qrtr.port numbers for port allocation
triggers a warning within idr_alloc() since the port number is cast
to int, and thus interpreted as a negative number. This leads to
the rejection of such valid port numbers in qrtr_port_assign() as
idr_alloc() fails.

To avoid the problem, switch to idr_alloc_u32() instead.

Fixes: bdabad3e36 ("net: Add Qualcomm IPC router")
Reported-by: syzbot+f31428628ef672716ea8@...kaller.appspotmail.com
Signed-off-by: Necip Fazil Yildiran <necip@...gle.com>
Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
---
v2:
* Use reverse christmas tree ordering for local variables
* Add reviewed-by tag
---
 net/qrtr/qrtr.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c
index b4c0db0b7d31..90c558f89d46 100644
--- a/net/qrtr/qrtr.c
+++ b/net/qrtr/qrtr.c
@@ -692,23 +692,25 @@ static void qrtr_port_remove(struct qrtr_sock *ipc)
  */
 static int qrtr_port_assign(struct qrtr_sock *ipc, int *port)
 {
+	u32 min_port;
 	int rc;
 
 	mutex_lock(&qrtr_port_lock);
 	if (!*port) {
-		rc = idr_alloc(&qrtr_ports, ipc,
-			       QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET + 1,
-			       GFP_ATOMIC);
-		if (rc >= 0)
-			*port = rc;
+		min_port = QRTR_MIN_EPH_SOCKET;
+		rc = idr_alloc_u32(&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)) {
 		rc = -EACCES;
 	} else if (*port == QRTR_PORT_CTRL) {
-		rc = idr_alloc(&qrtr_ports, ipc, 0, 1, GFP_ATOMIC);
+		min_port = 0;
+		rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, 0, GFP_ATOMIC);
 	} else {
-		rc = idr_alloc(&qrtr_ports, ipc, *port, *port + 1, GFP_ATOMIC);
-		if (rc >= 0)
-			*port = rc;
+		min_port = *port;
+		rc = idr_alloc_u32(&qrtr_ports, ipc, &min_port, *port, GFP_ATOMIC);
+		if (!rc)
+			*port = min_port;
 	}
 	mutex_unlock(&qrtr_port_lock);
 
-- 
2.28.0.220.ged08abb693-goog