git.openwrt.org Git - openwrt/staging/blocktrron.git/blob

   1 From e0f83d268974dab0361d11904dfc9acec53f96a6 Mon Sep 17 00:00:00 2001
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Fri, 11 Oct 2024 17:12:17 +0000
   4 Subject: [PATCH] genetlink: hold RCU in genlmsg_mcast()
   5
   6 [ Upstream commit 56440d7ec28d60f8da3bfa09062b3368ff9b16db ]
   7
   8 While running net selftests with CONFIG_PROVE_RCU_LIST=y I saw
   9 one lockdep splat [1].
  10
  11 genlmsg_mcast() uses for_each_net_rcu(), and must therefore hold RCU.
  12
  13 Instead of letting all callers guard genlmsg_multicast_allns()
  14 with a rcu_read_lock()/rcu_read_unlock() pair, do it in genlmsg_mcast().
  15
  16 This also means the @flags parameter is useless, we need to always use
  17 GFP_ATOMIC.
  18
  19 [1]
  20 [10882.424136] =============================
  21 [10882.424166] WARNING: suspicious RCU usage
  22 [10882.424309] 6.12.0-rc2-virtme #1156 Not tainted
  23 [10882.424400] -----------------------------
  24 [10882.424423] net/netlink/genetlink.c:1940 RCU-list traversed in non-reader section!!
  25 [10882.424469]
  26 other info that might help us debug this:
  27
  28 [10882.424500]
  29 rcu_scheduler_active = 2, debug_locks = 1
  30 [10882.424744] 2 locks held by ip/15677:
  31 [10882.424791] #0: ffffffffb6b491b0 (cb_lock){++++}-{3:3}, at: genl_rcv (net/netlink/genetlink.c:1219)
  32 [10882.426334] #1: ffffffffb6b49248 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg (net/netlink/genetlink.c:61 net/netlink/genetlink.c:57 net/netlink/genetlink.c:1209)
  33 [10882.426465]
  34 stack backtrace:
  35 [10882.426805] CPU: 14 UID: 0 PID: 15677 Comm: ip Not tainted 6.12.0-rc2-virtme #1156
  36 [10882.426919] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
  37 [10882.427046] Call Trace:
  38 [10882.427131]  <TASK>
  39 [10882.427244] dump_stack_lvl (lib/dump_stack.c:123)
  40 [10882.427335] lockdep_rcu_suspicious (kernel/locking/lockdep.c:6822)
  41 [10882.427387] genlmsg_multicast_allns (net/netlink/genetlink.c:1940 (discriminator 7) net/netlink/genetlink.c:1977 (discriminator 7))
  42 [10882.427436] l2tp_tunnel_notify.constprop.0 (net/l2tp/l2tp_netlink.c:119) l2tp_netlink
  43 [10882.427683] l2tp_nl_cmd_tunnel_create (net/l2tp/l2tp_netlink.c:253) l2tp_netlink
  44 [10882.427748] genl_family_rcv_msg_doit (net/netlink/genetlink.c:1115)
  45 [10882.427834] genl_rcv_msg (net/netlink/genetlink.c:1195 net/netlink/genetlink.c:1210)
  46 [10882.427877] ? __pfx_l2tp_nl_cmd_tunnel_create (net/l2tp/l2tp_netlink.c:186) l2tp_netlink
  47 [10882.427927] ? __pfx_genl_rcv_msg (net/netlink/genetlink.c:1201)
  48 [10882.427959] netlink_rcv_skb (net/netlink/af_netlink.c:2551)
  49 [10882.428069] genl_rcv (net/netlink/genetlink.c:1220)
  50 [10882.428095] netlink_unicast (net/netlink/af_netlink.c:1332 net/netlink/af_netlink.c:1357)
  51 [10882.428140] netlink_sendmsg (net/netlink/af_netlink.c:1901)
  52 [10882.428210] ____sys_sendmsg (net/socket.c:729 (discriminator 1) net/socket.c:744 (discriminator 1) net/socket.c:2607 (discriminator 1))
  53
  54 Fixes: 33f72e6f0c67 ("l2tp : multicast notification to the registered listeners")
  55 Signed-off-by: Eric Dumazet <edumazet@google.com>
  56 Cc: James Chapman <jchapman@katalix.com>
  57 Cc: Tom Parkin <tparkin@katalix.com>
  58 Cc: Johannes Berg <johannes.berg@intel.com>
  59 Link: https://patch.msgid.link/20241011171217.3166614-1-edumazet@google.com
  60 Signed-off-by: Jakub Kicinski <kuba@kernel.org>
  61 Signed-off-by: Sasha Levin <sashal@kernel.org>
  62 ---
  63  drivers/target/target_core_user.c |  2 +-
  64  include/net/genetlink.h           |  3 +--
  65  net/l2tp/l2tp_netlink.c           |  4 ++--
  66  net/netlink/genetlink.c           | 28 ++++++++++++++--------------
  67  net/wireless/nl80211.c            |  8 ++------
  68  5 files changed, 20 insertions(+), 25 deletions(-)
  69
  70 --- a/backport-include/net/genetlink.h
  71 +++ b/backport-include/net/genetlink.h
  72 @@ -150,7 +150,7 @@ int genlmsg_multicast(const struct genl_
  73  #define genlmsg_multicast_allns LINUX_BACKPORT(genlmsg_multicast_allns)
  74  int backport_genlmsg_multicast_allns(const struct genl_family *family,
  75                                      struct sk_buff *skb, u32 portid,
  76 -                                    unsigned int group, gfp_t flags);
  77 +                                    unsigned int group);
  78
  79  #define genl_family_attrbuf LINUX_BACKPORT(genl_family_attrbuf)
  80  static inline struct nlattr **genl_family_attrbuf(struct genl_family *family)
  81 --- a/compat/backport-genetlink.c
  82 +++ b/compat/backport-genetlink.c
  83 @@ -198,23 +198,23 @@ int genlmsg_multicast(const struct genl_
  84  }
  85  EXPORT_SYMBOL_GPL(genlmsg_multicast);
  86
  87 -static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group,
  88 -                        gfp_t flags)
  89 +static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group)
  90  {
  91         struct sk_buff *tmp;
  92         struct net *net, *prev = NULL;
  93         bool delivered = false;
  94         int err;
  95
  96 +       rcu_read_lock();
  97         for_each_net_rcu(net) {
  98                 if (prev) {
  99 -                       tmp = skb_clone(skb, flags);
 100 +                       tmp = skb_clone(skb, GFP_ATOMIC);
 101                         if (!tmp) {
 102                                 err = -ENOMEM;
 103                                 goto error;
 104                         }
 105                         err = nlmsg_multicast(prev->genl_sock, tmp,
 106 -                                             portid, group, flags);
 107 +                                             portid, group, GFP_ATOMIC);
 108                         if (!err)
 109                                 delivered = true;
 110                         else if (err != -ESRCH)
 111 @@ -223,25 +223,29 @@ static int genlmsg_mcast(struct sk_buff
 112
 113                 prev = net;
 114         }
 115 +       err = nlmsg_multicast(prev->genl_sock, skb, portid, group, GFP_ATOMIC);
 116 +
 117 +       rcu_read_unlock();
 118
 119 -       err = nlmsg_multicast(prev->genl_sock, skb, portid, group, flags);
 120         if (!err)
 121                 delivered = true;
 122         else if (err != -ESRCH)
 123                 return err;
 124         return delivered ? 0 : -ESRCH;
 125   error:
 126 +       rcu_read_unlock();
 127 +
 128         kfree_skb(skb);
 129         return err;
 130  }
 131
 132  int backport_genlmsg_multicast_allns(const struct genl_family *family,
 133                                      struct sk_buff *skb, u32 portid,
 134 -                                    unsigned int group, gfp_t flags)
 135 +                                    unsigned int group)
 136  {
 137         group = __backport_genl_group(family, group);
 138         if (group == INVALID_GROUP)
 139                 return -EINVAL;
 140 -       return genlmsg_mcast(skb, portid, group, flags);
 141 +       return genlmsg_mcast(skb, portid, group);
 142  }
 143  EXPORT_SYMBOL_GPL(backport_genlmsg_multicast_allns);
 144 --- a/net/wireless/nl80211.c
 145 +++ b/net/wireless/nl80211.c
 146 @@ -17956,10 +17956,8 @@ void nl80211_common_reg_change_event(enu
 147
 148         genlmsg_end(msg, hdr);
 149
 150 -       rcu_read_lock();
 151         genlmsg_multicast_allns(&nl80211_fam, msg, 0,
 152 -                               NL80211_MCGRP_REGULATORY, GFP_ATOMIC);
 153 -       rcu_read_unlock();
 154 +                               NL80211_MCGRP_REGULATORY);
 155
 156         return;
 157
 158 @@ -18692,10 +18690,8 @@ void nl80211_send_beacon_hint_event(stru
 159
 160         genlmsg_end(msg, hdr);
 161
 162 -       rcu_read_lock();
 163         genlmsg_multicast_allns(&nl80211_fam, msg, 0,
 164 -                               NL80211_MCGRP_REGULATORY, GFP_ATOMIC);
 165 -       rcu_read_unlock();
 166 +                               NL80211_MCGRP_REGULATORY);
 167
 168         return;
 169