Doug / smarc-fsl-linux-kernel

27 Jun, 2013

1 commit

  • 5dbe7c178   net: fix kernel deadlock with interface rename and netdev name retrieval. ... Browse Code »

    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

    Nicolas Schichan
     

19 Feb, 2013

1 commit