[PATCH net-next 00/14] net: annotate data-races around sysctl knobs

[Jiayuan Chen]

While testing the recent sysctl range fixes I noticed that a lot of our
sysctl knobs are read with plain loads while the handlers update them
with WRITE_ONCE() and no lock, so KCSAN reports them as data races. I
then used an LLM to go through every ctl_table under net/ and list the
readers that were left behind. This series annotates them with
READ_ONCE(), and adds WRITE_ONCE() to a few custom handlers and netlink
paths that store to the same fields with plain writes. Most of it is a
plain READ_ONCE() at each read; where a function reads the same knob
twice to make one decision, it now reads it once into a local, so the
comparison and the value it acts on cannot come from two different
writes.

There are no Fixes tags. Done one knob per patch this would be well over
a hundred commits, so I grouped them by subsystem and feature instead to
keep the review manageable. If maintainers prefer, I can split it up
further with a Fixes tag on each one, as several smaller series.

No functional change. KCSAN does hit these, e.g. toggling
net.ipv6.icmp.echo_ignore_all while receiving ICMPv6 echo requests:

  BUG: KCSAN: data-race in icmpv6_rcv / proc_dou8vec_minmax

  write (marked) to 0xffffffff8ee2940d of 1 bytes by task 504 on cpu 0:
   proc_dou8vec_minmax+0x1ab/0x1f0
   proc_sys_call_handler+0x282/0x3a0
   proc_sys_write+0x13/0x20
   ...

  read to 0xffffffff8ee2940d of 1 bytes by interrupt on cpu 3:
   icmpv6_rcv+0x99d/0xd40
   ip6_protocol_deliver_rcu+0x787/0x9a0
   ip6_input_finish+0xb0/0x1b0
   ip6_input+0xa8/0x250
   ipv6_rcv+0x14b/0x1c0
   ...

  value changed: 0x01 -> 0x00

Jiayuan Chen (14):
  ipv4: annotate data-races around ip_rt_* sysctls
  inet: frags: annotate data-races around fqdir->timeout and
    fqdir->max_dist
  ipv6: annotate data-races around addrconf sysctls
  ipv6: annotate data-races around icmpv6 reply sysctls
  calipso: annotate data-races around cache sysctls
  sctp: annotate data-races around sctp sysctls
  mptcp: annotate data-races around pernet sysctls
  rds: annotate data-races around core rds sysctls
  netfilter: conntrack: annotate data-races around conntrack sysctls
  netfilter: bridge: annotate data-races around br_netfilter and nf_log
    sysctls
  ipvs: annotate data-races around lblc_expiration and lblcr_expiration
  net/smc: annotate data-races around smc sysctls
  netfilter: conntrack: annotate data-races around timeout and tcp
    sysctls
  netfilter: cttimeout: annotate data-races around the default timeouts

 include/net/ipv6.h                            |   2 +-
 include/net/netfilter/nf_conntrack_acct.h     |   6 +-
 .../net/netfilter/nf_conntrack_timestamp.h    |   2 +-
 net/bridge/br_netfilter_hooks.c               |  20 ++--
 net/bridge/netfilter/ebt_log.c                |   2 +-
 net/ipv4/inet_fragment.c                      |   2 +-
 net/ipv4/ip_fragment.c                        |   6 +-
 net/ipv4/route.c                              |  34 +++---
 net/ipv6/addrconf.c                           |  22 ++--
 net/ipv6/calipso.c                            |   6 +-
 net/ipv6/icmp.c                               |  10 +-
 net/ipv6/ndisc.c                              |   2 +-
 net/ipv6/route.c                              |   8 +-
 net/mptcp/ctrl.c                              |  18 +--
 net/netfilter/ipvs/ip_vs_lblc.c               |   2 +-
 net/netfilter/ipvs/ip_vs_lblcr.c              |   2 +-
 net/netfilter/nf_conntrack_core.c             |   8 +-
 net/netfilter/nf_conntrack_ecache.c           |   2 +-
 net/netfilter/nf_conntrack_expect.c           |   2 +-
 net/netfilter/nf_conntrack_netlink.c          |   2 +-
 net/netfilter/nf_conntrack_proto.c            |   6 +-
 net/netfilter/nf_conntrack_proto_generic.c    |   8 +-
 net/netfilter/nf_conntrack_proto_gre.c        |  20 ++--
 net/netfilter/nf_conntrack_proto_icmp.c       |  12 +-
 net/netfilter/nf_conntrack_proto_icmpv6.c     |  12 +-
 net/netfilter/nf_conntrack_proto_sctp.c       |  13 ++-
 net/netfilter/nf_conntrack_proto_tcp.c        | 110 +++++++++---------
 net/netfilter/nf_conntrack_proto_udp.c        |  24 ++--
 net/netfilter/nf_flow_table_core.c            |   4 +-
 net/netfilter/nf_log_syslog.c                 |   2 +-
 net/rds/recv.c                                |   2 +-
 net/rds/send.c                                |   8 +-
 net/rds/threads.c                             |   4 +-
 net/sctp/associola.c                          |   2 +-
 net/sctp/bind_addr.c                          |   2 +-
 net/sctp/endpointola.c                        |  14 +--
 net/sctp/input.c                              |   2 +-
 net/sctp/sm_make_chunk.c                      |   6 +-
 net/sctp/sm_sideeffect.c                      |   2 +-
 net/sctp/sm_statefuns.c                       |   6 +-
 net/sctp/socket.c                             |  46 ++++----
 net/sctp/sysctl.c                             |  16 +--
 net/sctp/transport.c                          |   6 +-
 net/smc/af_smc.c                              |   8 +-
 net/smc/smc_clc.c                             |   8 +-
 net/smc/smc_core.c                            |   2 +-
 net/smc/smc_tx.c                              |   2 +-
 47 files changed, 259 insertions(+), 246 deletions(-)

-- 
2.43.0