[PATCH net 0/2] net: fix issues when uncloning an skb dst+metadata

[Antoine Tenart <atenart@kernel.org>]

Hi,

This fixes two issues when uncloning an skb dst+metadata in
tun_dst_unclone; this was initially reported by Vlad Buslov[1]. Because
of the memory leak fixed by patch 2, the issue in patch 1 never happened
in practice.

tun_dst_unclone is called from two different places, one in geneve/vxlan
to handle PMTU and one in net/openvswitch/actions.c where it is used to
retrieve tunnel information. While both Vlad and I tested the former, we
could not for the latter. I did spend quite some time trying to, but
that code path is not easy to trigger. Code inspection shows this should
be fine, the tunnel information (dst+metadata) is uncloned and the skb
it is referenced from is only consumed after all accesses to the tunnel
information are done:

  do_execute_actions
    output_userspace
      dev_fill_metadata_dst         <- dst+metadata is uncloned
      ovs_dp_upcall
        queue_userspace_packet
          ovs_nla_put_tunnel_info   <- metadata (tunnel info) is accessed
    consume_skb                     <- dst+metadata is freed

Thanks!
Antoine

[1] https://lore.kernel.org/all/ygnhh79yluw2.fsf@nvidia.com/T/#m2f814614a4f5424cea66bbff7297f692b59b69a0

Antoine Tenart (2):
  net: do not keep the dst cache when uncloning an skb dst and its
    metadata
  net: fix a memleak when uncloning an skb dst and its metadata

 include/net/dst_metadata.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

-- 
2.34.1