6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ Upstream commit 56440d7ec28d60f8da3bfa09062b3368ff9b16db ]
While running net selftests with CONFIG_PROVE_RCU_LIST=y I saw one lockdep splat [1].
genlmsg_mcast() uses for_each_net_rcu(), and must therefore hold RCU.
Instead of letting all callers guard genlmsg_multicast_allns() with a rcu_read_lock()/rcu_read_unlock() pair, do it in genlmsg_mcast().
This also means the @flags parameter is useless, we need to always use GFP_ATOMIC.
[1] [10882.424136] ============================= [10882.424166] WARNING: suspicious RCU usage [10882.424309] 6.12.0-rc2-virtme #1156 Not tainted [10882.424400] ----------------------------- [10882.424423] net/netlink/genetlink.c:1940 RCU-list traversed in non-reader section!! [10882.424469] other info that might help us debug this:
[10882.424500] rcu_scheduler_active = 2, debug_locks = 1 [10882.424744] 2 locks held by ip/15677: [10882.424791] #0: ffffffffb6b491b0 (cb_lock){++++}-{3:3}, at: genl_rcv (net/netlink/genetlink.c:1219) [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) [10882.426465] stack backtrace: [10882.426805] CPU: 14 UID: 0 PID: 15677 Comm: ip Not tainted 6.12.0-rc2-virtme #1156 [10882.426919] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [10882.427046] Call Trace: [10882.427131] <TASK> [10882.427244] dump_stack_lvl (lib/dump_stack.c:123) [10882.427335] lockdep_rcu_suspicious (kernel/locking/lockdep.c:6822) [10882.427387] genlmsg_multicast_allns (net/netlink/genetlink.c:1940 (discriminator 7) net/netlink/genetlink.c:1977 (discriminator 7)) [10882.427436] l2tp_tunnel_notify.constprop.0 (net/l2tp/l2tp_netlink.c:119) l2tp_netlink [10882.427683] l2tp_nl_cmd_tunnel_create (net/l2tp/l2tp_netlink.c:253) l2tp_netlink [10882.427748] genl_family_rcv_msg_doit (net/netlink/genetlink.c:1115) [10882.427834] genl_rcv_msg (net/netlink/genetlink.c:1195 net/netlink/genetlink.c:1210) [10882.427877] ? __pfx_l2tp_nl_cmd_tunnel_create (net/l2tp/l2tp_netlink.c:186) l2tp_netlink [10882.427927] ? __pfx_genl_rcv_msg (net/netlink/genetlink.c:1201) [10882.427959] netlink_rcv_skb (net/netlink/af_netlink.c:2551) [10882.428069] genl_rcv (net/netlink/genetlink.c:1220) [10882.428095] netlink_unicast (net/netlink/af_netlink.c:1332 net/netlink/af_netlink.c:1357) [10882.428140] netlink_sendmsg (net/netlink/af_netlink.c:1901) [10882.428210] ____sys_sendmsg (net/socket.c:729 (discriminator 1) net/socket.c:744 (discriminator 1) net/socket.c:2607 (discriminator 1))
Fixes: 33f72e6f0c67 ("l2tp : multicast notification to the registered listeners") Signed-off-by: Eric Dumazet edumazet@google.com Cc: James Chapman jchapman@katalix.com Cc: Tom Parkin tparkin@katalix.com Cc: Johannes Berg johannes.berg@intel.com Link: https://patch.msgid.link/20241011171217.3166614-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/target/target_core_user.c | 2 +- include/net/genetlink.h | 3 +-- net/l2tp/l2tp_netlink.c | 4 ++-- net/netlink/genetlink.c | 28 ++++++++++++++-------------- net/wireless/nl80211.c | 8 ++------ 5 files changed, 20 insertions(+), 25 deletions(-)
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c index 22cc6cac0ba2b..2e100b76914a0 100644 --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -2130,7 +2130,7 @@ static int tcmu_netlink_event_send(struct tcmu_dev *udev, }
ret = genlmsg_multicast_allns(&tcmu_genl_family, skb, 0, - TCMU_MCGRP_CONFIG, GFP_KERNEL); + TCMU_MCGRP_CONFIG);
/* Wait during an add as the listener may not be up yet */ if (ret == 0 || diff --git a/include/net/genetlink.h b/include/net/genetlink.h index c53244f204370..e8c34aa4a640d 100644 --- a/include/net/genetlink.h +++ b/include/net/genetlink.h @@ -478,13 +478,12 @@ static inline int genlmsg_multicast(const struct genl_family *family, * @skb: netlink message as socket buffer * @portid: own netlink portid to avoid sending to yourself * @group: offset of multicast group in groups array - * @flags: allocation flags * * This function must hold the RTNL or rcu_read_lock(). */ int genlmsg_multicast_allns(const struct genl_family *family, struct sk_buff *skb, u32 portid, - unsigned int group, gfp_t flags); + unsigned int group);
/** * genlmsg_unicast - unicast a netlink message diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c index a901fd14fe3bf..e27e00cb16c6b 100644 --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -115,7 +115,7 @@ static int l2tp_tunnel_notify(struct genl_family *family, NLM_F_ACK, tunnel, cmd);
if (ret >= 0) { - ret = genlmsg_multicast_allns(family, msg, 0, 0, GFP_ATOMIC); + ret = genlmsg_multicast_allns(family, msg, 0, 0); /* We don't care if no one is listening */ if (ret == -ESRCH) ret = 0; @@ -143,7 +143,7 @@ static int l2tp_session_notify(struct genl_family *family, NLM_F_ACK, session, cmd);
if (ret >= 0) { - ret = genlmsg_multicast_allns(family, msg, 0, 0, GFP_ATOMIC); + ret = genlmsg_multicast_allns(family, msg, 0, 0); /* We don't care if no one is listening */ if (ret == -ESRCH) ret = 0; diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c index d41c4a936ad0c..d6eee5140c8be 100644 --- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -1355,15 +1355,11 @@ static int genl_ctrl_event(int event, const struct genl_family *family, if (IS_ERR(msg)) return PTR_ERR(msg);
- if (!family->netnsok) { + if (!family->netnsok) genlmsg_multicast_netns(&genl_ctrl, &init_net, msg, 0, 0, GFP_KERNEL); - } else { - rcu_read_lock(); - genlmsg_multicast_allns(&genl_ctrl, msg, 0, - 0, GFP_ATOMIC); - rcu_read_unlock(); - } + else + genlmsg_multicast_allns(&genl_ctrl, msg, 0, 0);
return 0; } @@ -1752,23 +1748,23 @@ static int __init genl_init(void)
core_initcall(genl_init);
-static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group, - gfp_t flags) +static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group) { struct sk_buff *tmp; struct net *net, *prev = NULL; bool delivered = false; int err;
+ rcu_read_lock(); for_each_net_rcu(net) { if (prev) { - tmp = skb_clone(skb, flags); + tmp = skb_clone(skb, GFP_ATOMIC); if (!tmp) { err = -ENOMEM; goto error; } err = nlmsg_multicast(prev->genl_sock, tmp, - portid, group, flags); + portid, group, GFP_ATOMIC); if (!err) delivered = true; else if (err != -ESRCH) @@ -1777,27 +1773,31 @@ static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group,
prev = net; } + err = nlmsg_multicast(prev->genl_sock, skb, portid, group, GFP_ATOMIC); + + rcu_read_unlock();
- err = nlmsg_multicast(prev->genl_sock, skb, portid, group, flags); if (!err) delivered = true; else if (err != -ESRCH) return err; return delivered ? 0 : -ESRCH; error: + rcu_read_unlock(); + kfree_skb(skb); return err; }
int genlmsg_multicast_allns(const struct genl_family *family, struct sk_buff *skb, u32 portid, - unsigned int group, gfp_t flags) + unsigned int group) { if (WARN_ON_ONCE(group >= family->n_mcgrps)) return -EINVAL;
group = family->mcgrp_offset + group; - return genlmsg_mcast(skb, portid, group, flags); + return genlmsg_mcast(skb, portid, group); } EXPORT_SYMBOL(genlmsg_multicast_allns);
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 9e74f249cb45f..7979073036698 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -17905,10 +17905,8 @@ void nl80211_common_reg_change_event(enum nl80211_commands cmd_id,
genlmsg_end(msg, hdr);
- rcu_read_lock(); genlmsg_multicast_allns(&nl80211_fam, msg, 0, - NL80211_MCGRP_REGULATORY, GFP_ATOMIC); - rcu_read_unlock(); + NL80211_MCGRP_REGULATORY);
return;
@@ -18605,10 +18603,8 @@ void nl80211_send_beacon_hint_event(struct wiphy *wiphy,
genlmsg_end(msg, hdr);
- rcu_read_lock(); genlmsg_multicast_allns(&nl80211_fam, msg, 0, - NL80211_MCGRP_REGULATORY, GFP_ATOMIC); - rcu_read_unlock(); + NL80211_MCGRP_REGULATORY);
return;