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authorNicolas Schichan <nschichan@freebox.fr>2013-06-26 17:23:42 +0200
committerDavid S. Miller <davem@davemloft.net>2013-06-26 13:42:54 -0700
commit5dbe7c178d3f0a4634f088d9e729f1909b9ddcd1 (patch)
tree8945b6c5125b57cee5f36e903fc995e58664a639 /include
parent6d446ec32f169c6a5d9bc90684a8082a6cbe90f6 (diff)
net: fix kernel deadlock with interface rename and netdev name retrieval.
When the kernel (compiled with CONFIG_PREEMPT=n) is performing the rename of a network interface, it can end up waiting for a workqueue to complete. If userland is able to invoke a SIOCGIFNAME ioctl or a SO_BINDTODEVICE getsockopt in between, the kernel will deadlock due to the fact that read_secklock_begin() will spin forever waiting for the writer process (the one doing the interface rename) to update the devnet_rename_seq sequence. This patch fixes the problem by adding a helper (netdev_get_name()) and using it in the code handling the SIOCGIFNAME ioctl and SO_BINDTODEVICE setsockopt. The netdev_get_name() helper uses raw_seqcount_begin() to avoid spinning forever, waiting for devnet_rename_seq->sequence to become even. cond_resched() is used in the contended case, before retrying the access to give the writer process a chance to finish. The use of raw_seqcount_begin() will incur some unneeded work in the reader process in the contended case, but this is better than deadlocking the system. Signed-off-by: Nicolas Schichan <nschichan@freebox.fr> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/linux/netdevice.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 60584b185a0..96e4c21e15e 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1695,6 +1695,7 @@ extern int init_dummy_netdev(struct net_device *dev);
extern struct net_device *dev_get_by_index(struct net *net, int ifindex);
extern struct net_device *__dev_get_by_index(struct net *net, int ifindex);
extern struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);
+extern int netdev_get_name(struct net *net, char *name, int ifindex);
extern int dev_restart(struct net_device *dev);
#ifdef CONFIG_NETPOLL_TRAP
extern int netpoll_trap(void);