net: fix kernel deadlock with interface rename and netdev name retrieval.

2013-06-26T20:42:54Z

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 Acked-by: Eric Dumazet Signed-off-by: David S. Miller

net: move ioctl functions into a separated file

2013-02-18T17:27:32Z

They well deserve a separated unit. Cc: "David S. Miller" Signed-off-by: Cong Wang Signed-off-by: David S. Miller

linux/net/core/dev_ioctl.c, branch v3.12.10

net: fix kernel deadlock with interface rename and netdev name retrieval.

net: move ioctl functions into a separated file