diff options
| author | Stanislav Fomichev <sdf@google.com> | 2023-11-08 13:13:25 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2023-11-10 08:37:09 +0000 |
| commit | 871019b22d1bcc9fab2d1feba1b9a564acbb6e99 (patch) | |
| tree | bf9b093f9a016bad95b1ec384123e6a4ab3d3555 /net/ipv4 | |
| parent | 8a4f030dbced6fc255cbe67b2d0a129947e18493 (diff) | |
net: set SOCK_RCU_FREE before inserting socket into hashtable
We've started to see the following kernel traces:
WARNING: CPU: 83 PID: 0 at net/core/filter.c:6641 sk_lookup+0x1bd/0x1d0
Call Trace:
<IRQ>
__bpf_skc_lookup+0x10d/0x120
bpf_sk_lookup+0x48/0xd0
bpf_sk_lookup_tcp+0x19/0x20
bpf_prog_<redacted>+0x37c/0x16a3
cls_bpf_classify+0x205/0x2e0
tcf_classify+0x92/0x160
__netif_receive_skb_core+0xe52/0xf10
__netif_receive_skb_list_core+0x96/0x2b0
napi_complete_done+0x7b5/0xb70
<redacted>_poll+0x94/0xb0
net_rx_action+0x163/0x1d70
__do_softirq+0xdc/0x32e
asm_call_irq_on_stack+0x12/0x20
</IRQ>
do_softirq_own_stack+0x36/0x50
do_softirq+0x44/0x70
__inet_hash can race with lockless (rcu) readers on the other cpus:
__inet_hash
__sk_nulls_add_node_rcu
<- (bpf triggers here)
sock_set_flag(SOCK_RCU_FREE)
Let's move the SOCK_RCU_FREE part up a bit, before we are inserting
the socket into hashtables. Note, that the race is really harmless;
the bpf callers are handling this situation (where listener socket
doesn't have SOCK_RCU_FREE set) correctly, so the only
annoyance is a WARN_ONCE.
More details from Eric regarding SOCK_RCU_FREE timeline:
Commit 3b24d854cb35 ("tcp/dccp: do not touch listener sk_refcnt under
synflood") added SOCK_RCU_FREE. At that time, the precise location of
sock_set_flag(sk, SOCK_RCU_FREE) did not matter, because the thread calling
__inet_hash() owns a reference on sk. SOCK_RCU_FREE was only tested
at dismantle time.
Commit 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF")
started checking SOCK_RCU_FREE _after_ the lookup to infer whether
the refcount has been taken care of.
Fixes: 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/inet_hashtables.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index 598c1b114d2c..a532f749e477 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -751,12 +751,12 @@ int __inet_hash(struct sock *sk, struct sock *osk) if (err) goto unlock; } + sock_set_flag(sk, SOCK_RCU_FREE); if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport && sk->sk_family == AF_INET6) __sk_nulls_add_node_tail_rcu(sk, &ilb2->nulls_head); else __sk_nulls_add_node_rcu(sk, &ilb2->nulls_head); - sock_set_flag(sk, SOCK_RCU_FREE); sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1); unlock: spin_unlock(&ilb2->lock); |