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authorDmitry Safonov <0x7f454c46@gmail.com>2024-08-01 01:13:28 +0100
committerDavid S. Miller <davem@davemloft.net>2024-08-04 13:21:50 +0100
commit14ab4792ee120c022f276a7e4768f4dcb08f0cdd (patch)
treeb1489837d670d58b5e7ed685cebea8da50e74853 /net
parentfba917b169bea5f8f2ee300e19d5f7a6341a5251 (diff)
net/tcp: Disable TCP-AO static key after RCU grace period
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(). See the comment near the definition: > * The caller must make sure that the static key can't get disabled while > * in this function. It doesn't patch jump labels, only adds a user to > * an already enabled static key. Originally it was introduced in commit eb8c507296f6 ("jump_label: Prevent key->enabled int overflow"), which is needed for the atomic contexts, one of which would be the creation of a full socket from a request socket. In that atomic context, it's known by the presence of the key (md5/ao) that the static branch is already enabled. So, the ref counter for that static branch is just incremented instead of holding the proper mutex. static_key_fast_inc_not_disabled() is just a helper for such usage case. But it must not be used if the static branch could get disabled in parallel as it's not protected by jump_label_mutex and as a result, races with jump_label_update() implementation details. 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@kernel.org Fixes: 67fa83f7c86a ("net/tcp: Add static_key for TCP-AO") Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_ao.c43
1 files changed, 30 insertions, 13 deletions
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 85531437890c..db6516092daf 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -267,32 +267,49 @@ static void tcp_ao_key_free_rcu(struct rcu_head *head)
kfree_sensitive(key);
}
-void tcp_ao_destroy_sock(struct sock *sk, bool twsk)
+static void tcp_ao_info_free_rcu(struct rcu_head *head)
{
- struct tcp_ao_info *ao;
+ struct tcp_ao_info *ao = container_of(head, struct tcp_ao_info, rcu);
struct tcp_ao_key *key;
struct hlist_node *n;
+ hlist_for_each_entry_safe(key, n, &ao->head, node) {
+ hlist_del(&key->node);
+ tcp_sigpool_release(key->tcp_sigpool_id);
+ kfree_sensitive(key);
+ }
+ kfree(ao);
+ static_branch_slow_dec_deferred(&tcp_ao_needed);
+}
+
+static void tcp_ao_sk_omem_free(struct sock *sk, struct tcp_ao_info *ao)
+{
+ size_t total_ao_sk_mem = 0;
+ struct tcp_ao_key *key;
+
+ hlist_for_each_entry(key, &ao->head, node)
+ total_ao_sk_mem += tcp_ao_sizeof_key(key);
+ atomic_sub(total_ao_sk_mem, &sk->sk_omem_alloc);
+}
+
+void tcp_ao_destroy_sock(struct sock *sk, bool twsk)
+{
+ struct tcp_ao_info *ao;
+
if (twsk) {
ao = rcu_dereference_protected(tcp_twsk(sk)->ao_info, 1);
- tcp_twsk(sk)->ao_info = NULL;
+ rcu_assign_pointer(tcp_twsk(sk)->ao_info, NULL);
} else {
ao = rcu_dereference_protected(tcp_sk(sk)->ao_info, 1);
- tcp_sk(sk)->ao_info = NULL;
+ rcu_assign_pointer(tcp_sk(sk)->ao_info, NULL);
}
if (!ao || !refcount_dec_and_test(&ao->refcnt))
return;
- hlist_for_each_entry_safe(key, n, &ao->head, node) {
- hlist_del_rcu(&key->node);
- if (!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);
+ if (!twsk)
+ tcp_ao_sk_omem_free(sk, ao);
+ call_rcu(&ao->rcu, tcp_ao_info_free_rcu);
}
void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, struct tcp_sock *tp)