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authorEric Dumazet <edumazet@google.com>2024-10-11 17:12:17 +0000
committerJakub Kicinski <kuba@kernel.org>2024-10-15 17:52:58 -0700
commit56440d7ec28d60f8da3bfa09062b3368ff9b16db (patch)
tree92b21605eafbbc3aa6ab37834a3614a0e6e73b41 /net/netlink
parent1833d8a26f057128fd63e126b4428203ece84684 (diff)
genetlink: hold RCU in genlmsg_mcast()
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>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/genetlink.c28
1 files changed, 14 insertions, 14 deletions
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index feb54c63a116..07ad65774fe2 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1501,15 +1501,11 @@ 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;
}
@@ -1929,23 +1925,23 @@ problem:
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)
@@ -1954,27 +1950,31 @@ 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);