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net: add rcu locking when changing early demux

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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: dddb64bcb3 ("net: Add sysctl to toggle early demux for tcp and udp")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2017-04-22 09:33:16 -07:00 committed by David S. Miller
parent ad0cb27ce9
commit 58c4c6a3f7
1 changed files with 3 additions and 0 deletions
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3
net/ipv4/sysctl_net_ipv4.c
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@ -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,