[PATCH net] net/tcp: Disable TCP-AO static key after RCU grace period
From: Dmitry Safonov via B4 Relay
Date: Thu Jul 25 2024 - 01:00:24 EST
From: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
The lifetime of TCP-AO static_key is the same as the last
tcp_ao_info. On the socket destruction tcp_ao_info ceases to be
with RCU grace period, while tcp-ao static branch is currently deferred
destructed. The static key definition is
: DEFINE_STATIC_KEY_DEFERRED_FALSE(tcp_ao_needed, HZ);
which means that if RCU grace period is delayed by more than a second
and tcp_ao_needed is in the process of disablement, other CPUs may
yet see tcp_ao_info which atent dead, but soon-to-be.
And that breaks the assumption of static_key_fast_inc_not_disabled().
Happened on netdev test-bot[1], so not a theoretical issue:
[] jump_label: Fatal kernel bug, unexpected op at tcp_inbound_hash+0x1a7/0x870 [ffffffffa8c4e9b7] (eb 50 0f 1f 44 != 66 90 0f 1f 00)) size:2 type:1
[] ------------[ cut here ]------------
[] kernel BUG at arch/x86/kernel/jump_label.c:73!
[] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
[] CPU: 3 PID: 243 Comm: kworker/3:3 Not tainted 6.10.0-virtme #1
[] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[] Workqueue: events jump_label_update_timeout
[] RIP: 0010:__jump_label_patch+0x2f6/0x350
...
[] Call Trace:
[] <TASK>
[] arch_jump_label_transform_queue+0x6c/0x110
[] __jump_label_update+0xef/0x350
[] __static_key_slow_dec_cpuslocked.part.0+0x3c/0x60
[] jump_label_update_timeout+0x2c/0x40
[] process_one_work+0xe3b/0x1670
[] worker_thread+0x587/0xce0
[] kthread+0x28a/0x350
[] ret_from_fork+0x31/0x70
[] ret_from_fork_asm+0x1a/0x30
[] </TASK>
[] Modules linked in: veth
[] ---[ end trace 0000000000000000 ]---
[] RIP: 0010:__jump_label_patch+0x2f6/0x350
[1]: https://netdev-3.bots.linux.dev/vmksft-tcp-ao-dbg/results/696681/5-connect-deny-ipv6/stderr
Cc: stable@xxxxxxxxxx
Fixes: 67fa83f7c86a ("net/tcp: Add static_key for TCP-AO")
Signed-off-by: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
---
---
net/ipv4/tcp_ao.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 85531437890c..5ce914d3e3db 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -267,6 +267,14 @@ static void tcp_ao_key_free_rcu(struct rcu_head *head)
kfree_sensitive(key);
}
+static void tcp_ao_info_free_rcu(struct rcu_head *head)
+{
+ struct tcp_ao_info *ao = container_of(head, struct tcp_ao_info, rcu);
+
+ kfree(ao);
+ static_branch_slow_dec_deferred(&tcp_ao_needed);
+}
+
void tcp_ao_destroy_sock(struct sock *sk, bool twsk)
{
struct tcp_ao_info *ao;
@@ -290,9 +298,7 @@ void tcp_ao_destroy_sock(struct sock *sk, bool twsk)
atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc);
call_rcu(&key->rcu, tcp_ao_key_free_rcu);
}
-
- kfree_rcu(ao, rcu);
- static_branch_slow_dec_deferred(&tcp_ao_needed);
+ call_rcu(&ao->rcu, tcp_ao_info_free_rcu);
}
void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, struct tcp_sock *tp)
---
base-commit: c33ffdb70cc6df4105160f991288e7d2567d7ffa
change-id: 20240725-tcp-ao-static-branch-rcu-85ede7b3a1a5
Best regards,
--
Dmitry Safonov <0x7f454c46@xxxxxxxxx>