6.10-stable review patch. If anyone has any objections, please let me know.
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From: Dmitry Safonov 0x7f454c46@gmail.com
commit 14ab4792ee120c022f276a7e4768f4dcb08f0cdd upstream.
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-d...
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp_ao.c | 43 ++++++++++++++++++++++++++++++------------- 1 file changed, 30 insertions(+), 13 deletions(-)
--- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -266,32 +266,49 @@ static void tcp_ao_key_free_rcu(struct r 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)