systemd-sysctl is triggering a suspicious RCU usage message when
net.ipv4.tcp_early_demux or net.ipv4.udp_early_demux is changed via
a sysctl config file:
[ 33.896184] ===============================
[ 33.899558] [ ERR: suspicious RCU usage. ]
[ 33.900624] 4.11.0-rc7+ #104 Not tainted
[ 33.901698] -------------------------------
[ 33.903059] /home/dsa/kernel-2.git/net/ipv4/sysctl_net_ipv4.c:305 suspicious
rcu_dereference_check() usage!
[ 33.905724]
other info that might help us debug this:
[ 33.907656]
rcu_scheduler_active = 2, debug_locks = 0
[ 33.909288] 1 lock held by systemd-sysctl/143:
[ 33.910373] #0: (sb_writers#5){.+.+.+}, at: [<ffffffff8123a370>]
file_start_write+0x45/0x48
[ 33.912407]
stack backtrace:
[ 33.914018] CPU: 0 PID: 143 Comm: systemd-sysctl Not tainted 4.11.0-rc7+ #104
[ 33.915631] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.7.5-20140531_083030-gandalf 04/01/2014
[ 33.917870] Call Trace:
[ 33.918431] dump_stack+0x81/0xb6
[ 33.919241] lockdep_rcu_suspicious+0x10f/0x118
[ 33.920263] proc_configure_early_demux+0x65/0x10a
[ 33.921391] proc_udp_early_demux+0x3a/0x41
add rcu locking to proc_configure_early_demux.
Fixes: dddb64bcb3461 ("net: Add sysctl to toggle early demux for tcp and udp")
Signed-off-by: David Ahern <d...@cumulusnetworks.com>
---
net/ipv4/sysctl_net_ipv4.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 6fb25693c00b..ddac9e64b702 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -302,6 +302,8 @@ static void proc_configure_early_demux(int enabled, int
protocol)
struct inet6_protocol *ip6prot;
#endif
+ rcu_read_lock();
+
ipprot = rcu_dereference(inet_protos[protocol]);
if (ipprot)
ipprot->early_demux = enabled ? ipprot->early_demux_handler :
@@ -313,6 +315,7 @@ static void proc_configure_early_demux(int enabled, int
protocol)
ip6prot->early_demux = enabled ? ip6prot->early_demux_handler :
NULL;
#endif
+ rcu_read_unlock();
}
static int proc_tcp_early_demux(struct ctl_table *table, int write,
--
2.1.4
