Jakub Kicinski wrote:
> On Thu, 09 May 2019 21:57:49 -0700, John Fastabend wrote:
[...]
>
> Looks like David Beckett managed to trigger another nasty on the
> release path :/
>
> BUG: kernel NULL pointer dereference, address: 0000000000000012
> PGD 0 P4D 0
> Oops: 0000 [#1] SMP PTI
> CPU: 7 PID: 0 Comm: swapper/7 Not tainted
> 5.2.0-rc1-00139-g14629453a6d3 #21 RIP: 0010:tcp_peek_len+0x10/0x60
> RSP: 0018:ffffc02e41c54b98 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff9cf924c4e030 RCX: 0000000000000051
> RDX: 0000000000000000 RSI: 000000000000000c RDI: ffff9cf97128f480
> RBP: ffff9cf9365e0300 R08: ffff9cf94fe7d2c0 R09: 0000000000000000
> R10: 000000000000036b R11: ffff9cf939735e00 R12: ffff9cf91ad9ae40
> R13: ffff9cf924c4e000 R14: ffff9cf9a8fcbaae R15: 0000000000000020
> FS: 0000000000000000(0000) GS:ffff9cf9af7c0000(0000)
> knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0:
> 0000000080050033 CR2: 0000000000000012 CR3: 000000013920a003 CR4:
> 00000000003606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> 0000000000000400 Call Trace:
> <IRQ>
> strp_data_ready+0x48/0x90
> tls_data_ready+0x22/0xd0 [tls]
> tcp_rcv_established+0x569/0x620
> tcp_v4_do_rcv+0x127/0x1e0
> tcp_v4_rcv+0xad7/0xbf0
> ip_protocol_deliver_rcu+0x2c/0x1c0
> ip_local_deliver_finish+0x41/0x50
> ip_local_deliver+0x6b/0xe0
> ? ip_protocol_deliver_rcu+0x1c0/0x1c0
> ip_rcv+0x52/0xd0
> ? ip_rcv_finish_core.isra.20+0x380/0x380
> __netif_receive_skb_one_core+0x7e/0x90
> netif_receive_skb_internal+0x42/0xf0
> napi_gro_receive+0xed/0x150
> nfp_net_poll+0x7a2/0xd30 [nfp]
> ? kmem_cache_free_bulk+0x286/0x310
> net_rx_action+0x149/0x3b0
> __do_softirq+0xe3/0x30a
> ? handle_irq_event_percpu+0x6a/0x80
> irq_exit+0xe8/0xf0
> do_IRQ+0x85/0xd0
> common_interrupt+0xf/0xf
> </IRQ>
> RIP: 0010:cpuidle_enter_state+0xbc/0x450
>
> If I read this right strparser calls sock->ops->peek_len(sock), but the
> sock->sk is already NULL. I'm guess this is because inet_release()
> does:
>
> sock->sk = NULL;
> sk->sk_prot->close(sk, timeout);
>
> And I don't really see a way for ktls to know that sock->sk is about to
> be cleared, and therefore no way to stop strparser. Or for strparser
> to always do the check, given tcp_peek_len() will do another dereference
> of sock->sk :S
>
> That's mostly a guess, it takes me half an hour of ktls connections
> running to repro.
>
> Any advice would be appreciated.. Can we move the sock->sk assignment
> after close?..
>
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index 5183a2daba64..aff93e7cdb31 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -428,8 +428,8 @@ int inet_release(struct socket *sock)
> if (sock_flag(sk, SOCK_LINGER) &&
> !(current->flags & PF_EXITING))
> timeout = sk->sk_lingertime;
> - sock->sk = NULL;
> sk->sk_prot->close(sk, timeout);
> + sock->sk = NULL;
> }
> return 0;
> }
>
> I don't see IPv6 clearing this pointer, perhaps we don't have to?
> We tested it and it seems to works, but this is pre-git code, so
> it's hard to tell what the reason to clear was :)
How about making strp_peek_len tolerant of a null sock->sk?
diff --git a/net/strparser/strparser.c b/net/strparser/strparser.c
index e137698e8aef..79518f93d2d8 100644
--- a/net/strparser/strparser.c
+++ b/net/strparser/strparser.c
@@ -84,9 +84,10 @@ static void strp_parser_err(struct strparser *strp, int err,
static inline int strp_peek_len(struct strparser *strp)
{
if (strp->sk) {
- struct socket *sock = strp->sk->sk_socket;
+ struct socket *sock = READ_ONCE(strp->sk->sk_socket);
- return sock->ops->peek_len(sock);
+ if (likely(sock))
+ return sock->ops->peek_len(sock);
}
