[PATCH 4.19 14/41] netrom: Fix data-races around sysctl_netrom_network_ttl_initialiser

[Sasha Levin <sashal@kernel.org>]

From: Jason Xing <kernelxing@tencent.com>

[ Upstream commit 119cae5ea3f9e35cdada8e572cc067f072fa825a ]

We need to protect the reader reading the sysctl value because the
value can be changed concurrently.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/netrom/nr_dev.c  | 2 +-
 net/netrom/nr_out.c  | 2 +-
 net/netrom/nr_subr.c | 5 +++--
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/netrom/nr_dev.c b/net/netrom/nr_dev.c
index 988f542481a83..fa845edad7bf6 100644
--- a/net/netrom/nr_dev.c
+++ b/net/netrom/nr_dev.c
@@ -84,7 +84,7 @@ static int nr_header(struct sk_buff *skb, struct net_device *dev,
 	buff[6] |= AX25_SSSID_SPARE;
 	buff    += AX25_ADDR_LEN;
 
-	*buff++ = sysctl_netrom_network_ttl_initialiser;
+	*buff++ = READ_ONCE(sysctl_netrom_network_ttl_initialiser);
 
 	*buff++ = NR_PROTO_IP;
 	*buff++ = NR_PROTO_IP;
diff --git a/net/netrom/nr_out.c b/net/netrom/nr_out.c
index 00fbf1419ec6b..213bddab6e74f 100644
--- a/net/netrom/nr_out.c
+++ b/net/netrom/nr_out.c
@@ -207,7 +207,7 @@ void nr_transmit_buffer(struct sock *sk, struct sk_buff *skb)
 	dptr[6] |= AX25_SSSID_SPARE;
 	dptr += AX25_ADDR_LEN;
 
-	*dptr++ = sysctl_netrom_network_ttl_initialiser;
+	*dptr++ = READ_ONCE(sysctl_netrom_network_ttl_initialiser);
 
 	if (!nr_route_frame(skb, NULL)) {
 		kfree_skb(skb);
diff --git a/net/netrom/nr_subr.c b/net/netrom/nr_subr.c
index a7d3a265befb9..b5cee72b8c985 100644
--- a/net/netrom/nr_subr.c
+++ b/net/netrom/nr_subr.c
@@ -185,7 +185,8 @@ void nr_write_internal(struct sock *sk, int frametype)
 		*dptr++ = nr->my_id;
 		*dptr++ = frametype;
 		*dptr++ = nr->window;
-		if (nr->bpqext) *dptr++ = sysctl_netrom_network_ttl_initialiser;
+		if (nr->bpqext)
+			*dptr++ = READ_ONCE(sysctl_netrom_network_ttl_initialiser);
 		break;
 
 	case NR_DISCREQ:
@@ -239,7 +240,7 @@ void __nr_transmit_reply(struct sk_buff *skb, int mine, unsigned char cmdflags)
 	dptr[6] |= AX25_SSSID_SPARE;
 	dptr += AX25_ADDR_LEN;
 
-	*dptr++ = sysctl_netrom_network_ttl_initialiser;
+	*dptr++ = READ_ONCE(sysctl_netrom_network_ttl_initialiser);
 
 	if (mine) {
 		*dptr++ = 0;
-- 
2.43.0