From ccf434380d1a67df2dcb9113206b77d0cb0a1cef Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 26 Jan 2011 18:08:02 +0000
Subject: [PATCH] net: fix dev_seq_next()
Commit c6d14c84566d (net: Introduce for_each_netdev_rcu() iterator)
added a race in dev_seq_next().
The rcu_dereference() call should be done _before_ testing the end of
list, or we might return a wrong net_device if a concurrent thread
changes net_device list under us.
Note : discovered thanks to a sparse warning :
net/core/dev.c:3919:9: error: incompatible types in comparison expression
(different address spaces)
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
include/linux/netdevice.h | 9 ++++++++-
net/core/dev.c | 11 +++++++----
2 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8858422c5c5d..c7d707452228 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1447,7 +1447,7 @@ static inline struct net_device *next_net_device_rcu(struct net_device *dev)
struct net *net;
net = dev_net(dev);
- lh = rcu_dereference(dev->dev_list.next);
+ lh = rcu_dereference(list_next_rcu(&dev->dev_list));
return lh == &net->dev_base_head ? NULL : net_device_entry(lh);
}
@@ -1457,6 +1457,13 @@ static inline struct net_device *first_net_device(struct net *net)
net_device_entry(net->dev_base_head.next);
}
+static inline struct net_device *first_net_device_rcu(struct net *net)
+{
+ struct list_head *lh = rcu_dereference(list_next_rcu(&net->dev_base_head));
+
+ return lh == &net->dev_base_head ? NULL : net_device_entry(lh);
+}
+
extern int netdev_boot_setup_check(struct net_device *dev);
extern unsigned long netdev_boot_base(const char *prefix, int unit);
extern struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
diff --git a/net/core/dev.c b/net/core/dev.c
index 1b4c07fe295f..ddd5df2b61d4 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4051,12 +4051,15 @@ void *dev_seq_start(struct seq_file *seq, loff_t *pos)
void *dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
- struct net_device *dev = (v == SEQ_START_TOKEN) ?
- first_net_device(seq_file_net(seq)) :
- next_net_device((struct net_device *)v);
+ struct net_device *dev = v;
+
+ if (v == SEQ_START_TOKEN)
+ dev = first_net_device_rcu(seq_file_net(seq));
+ else
+ dev = next_net_device_rcu(dev);
++*pos;
- return rcu_dereference(dev);
+ return dev;
}
void dev_seq_stop(struct seq_file *seq, void *v)
--
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