[PATCH net] tcp: fix another uninit-value (sk_rx_queue_mapping)

[Eric Dumazet]

From: Eric Dumazet <edum...@google.com>

KMSAN is still not happy [1].

I missed that passive connections do not inherit their
sk_rx_queue_mapping values from the request socket,
but instead tcp_child_process() is calling
sk_mark_napi_id(child, skb)

We have many sk_mark_napi_id() callers, so I am providing
a new helper, forcing the setting sk_rx_queue_mapping
and sk_napi_id.

Note that we had no KMSAN report for sk_napi_id because
passive connections got a copy of this field from the listener.
sk_rx_queue_mapping in the other hand is inside the
sk_dontcopy_begin/sk_dontcopy_end so sk_clone_lock()
leaves this field uninitialized.

We might remove dead code populating req->sk_rx_queue_mapping
in the future.

[1]

BUG: KMSAN: uninit-value in __sk_rx_queue_set include/net/sock.h:1924 [inline]
BUG: KMSAN: uninit-value in sk_rx_queue_update include/net/sock.h:1938 [inline]
BUG: KMSAN: uninit-value in sk_mark_napi_id include/net/busy_poll.h:136 [inline]
BUG: KMSAN: uninit-value in tcp_child_process+0xb42/0x1050 net/ipv4/tcp_minisocks.c:833
__sk_rx_queue_set include/net/sock.h:1924 [inline]
sk_rx_queue_update include/net/sock.h:1938 [inline]
sk_mark_napi_id include/net/busy_poll.h:136 [inline]
tcp_child_process+0xb42/0x1050 net/ipv4/tcp_minisocks.c:833
tcp_v4_rcv+0x3d83/0x4ed0 net/ipv4/tcp_ipv4.c:2066
ip_protocol_deliver_rcu+0x760/0x10b0 net/ipv4/ip_input.c:204
ip_local_deliver_finish net/ipv4/ip_input.c:231 [inline]
NF_HOOK include/linux/netfilter.h:307 [inline]
ip_local_deliver+0x584/0x8c0 net/ipv4/ip_input.c:252
dst_input include/net/dst.h:460 [inline]
ip_sublist_rcv_finish net/ipv4/ip_input.c:551 [inline]
ip_list_rcv_finish net/ipv4/ip_input.c:601 [inline]
ip_sublist_rcv+0x11fd/0x1520 net/ipv4/ip_input.c:609
ip_list_rcv+0x95f/0x9a0 net/ipv4/ip_input.c:644
__netif_receive_skb_list_ptype net/core/dev.c:5505 [inline]
__netif_receive_skb_list_core+0xe34/0x1240 net/core/dev.c:5553
__netif_receive_skb_list+0x7fc/0x960 net/core/dev.c:5605
netif_receive_skb_list_internal+0x868/0xde0 net/core/dev.c:5696
gro_normal_list net/core/dev.c:5850 [inline]
napi_complete_done+0x579/0xdd0 net/core/dev.c:6587
virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline]
virtnet_poll+0x17b6/0x2350 drivers/net/virtio_net.c:1557
__napi_poll+0x14e/0xbc0 net/core/dev.c:7020
napi_poll net/core/dev.c:7087 [inline]
net_rx_action+0x824/0x1880 net/core/dev.c:7174
__do_softirq+0x1fe/0x7eb kernel/softirq.c:558
run_ksoftirqd+0x33/0x50 kernel/softirq.c:920
smpboot_thread_fn+0x616/0xbf0 kernel/smpboot.c:164
kthread+0x721/0x850 kernel/kthread.c:327
ret_from_fork+0x1f/0x30

Uninit was created at:
__alloc_pages+0xbc7/0x10a0 mm/page_alloc.c:5409
alloc_pages+0x8a5/0xb80
alloc_slab_page mm/slub.c:1810 [inline]
allocate_slab+0x287/0x1c20 mm/slub.c:1947
new_slab mm/slub.c:2010 [inline]
___slab_alloc+0xbdf/0x1e90 mm/slub.c:3039
__slab_alloc mm/slub.c:3126 [inline]
slab_alloc_node mm/slub.c:3217 [inline]
slab_alloc mm/slub.c:3259 [inline]
kmem_cache_alloc+0xbb3/0x11c0 mm/slub.c:3264
sk_prot_alloc+0xeb/0x570 net/core/sock.c:1914
sk_clone_lock+0xd6/0x1940 net/core/sock.c:2118
inet_csk_clone_lock+0x8d/0x6a0 net/ipv4/inet_connection_sock.c:956
tcp_create_openreq_child+0xb1/0x1ef0 net/ipv4/tcp_minisocks.c:453
tcp_v4_syn_recv_sock+0x268/0x2710 net/ipv4/tcp_ipv4.c:1563
tcp_check_req+0x207c/0x2a30 net/ipv4/tcp_minisocks.c:765
tcp_v4_rcv+0x36f5/0x4ed0 net/ipv4/tcp_ipv4.c:2047
ip_protocol_deliver_rcu+0x760/0x10b0 net/ipv4/ip_input.c:204
ip_local_deliver_finish net/ipv4/ip_input.c:231 [inline]
NF_HOOK include/linux/netfilter.h:307 [inline]
ip_local_deliver+0x584/0x8c0 net/ipv4/ip_input.c:252
dst_input include/net/dst.h:460 [inline]
ip_sublist_rcv_finish net/ipv4/ip_input.c:551 [inline]
ip_list_rcv_finish net/ipv4/ip_input.c:601 [inline]
ip_sublist_rcv+0x11fd/0x1520 net/ipv4/ip_input.c:609
ip_list_rcv+0x95f/0x9a0 net/ipv4/ip_input.c:644
__netif_receive_skb_list_ptype net/core/dev.c:5505 [inline]
__netif_receive_skb_list_core+0xe34/0x1240 net/core/dev.c:5553
__netif_receive_skb_list+0x7fc/0x960 net/core/dev.c:5605
netif_receive_skb_list_internal+0x868/0xde0 net/core/dev.c:5696
gro_normal_list net/core/dev.c:5850 [inline]
napi_complete_done+0x579/0xdd0 net/core/dev.c:6587
virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline]
virtnet_poll+0x17b6/0x2350 drivers/net/virtio_net.c:1557
__napi_poll+0x14e/0xbc0 net/core/dev.c:7020
napi_poll net/core/dev.c:7087 [inline]
net_rx_action+0x824/0x1880 net/core/dev.c:7174
__do_softirq+0x1fe/0x7eb kernel/softirq.c:558

Fixes: 342159ee394d ("net: avoid dirtying sk->sk_rx_queue_mapping")
Fixes: a37a0ee4d25c ("net: avoid uninit-value from tcp_conn_request")
Signed-off-by: Eric Dumazet <edum...@google.com>
Reported-by: syzbot <syzk...@googlegroups.com>
---
include/net/busy_poll.h | 13 +++++++++++++
net/ipv4/tcp_minisocks.c | 4 ++--
2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 7994455ec714610fbcb563d8c7a1411b02201e05..c4898fcbf923bf01f14c6bcc694eb036d75d7195 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -136,6 +136,19 @@ static inline void sk_mark_napi_id(struct sock *sk, const struct sk_buff *skb)
sk_rx_queue_update(sk, skb);
}

+/* Variant of sk_mark_napi_id() for passive flow setup,
+ * as sk->sk_napi_id and sk->sk_rx_queue_mapping content
+ * needs to be set.
+ */
+static inline void sk_mark_napi_id_set(struct sock *sk,
+ const struct sk_buff *skb)
+{
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ WRITE_ONCE(sk->sk_napi_id, skb->napi_id);
+#endif
+ sk_rx_queue_set(sk, skb);
+}
+
static inline void __sk_mark_napi_id_once(struct sock *sk, unsigned int napi_id)
{
#ifdef CONFIG_NET_RX_BUSY_POLL
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index cf913a66df17023bbab8b42e313ce646858c268a..7c2d3ac2363acebcfd92d7a4886c052c8aa120b9 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -829,8 +829,8 @@ int tcp_child_process(struct sock *parent, struct sock *child,
int ret = 0;
int state = child->sk_state;

- /* record NAPI ID of child */
- sk_mark_napi_id(child, skb);
+ /* record sk_napi_id and sk_rx_queue_mapping of child. */
+ sk_mark_napi_id_set(child, skb);

tcp_segs_in(tcp_sk(child), skb);
if (!sock_owned_by_user(child)) {
--
2.34.1.400.ga245620fadb-goog

[Alexander Potapenko]

Tested-by: Alexander Potapenko <gli...@google.com>

syzbot is happy now.

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--
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
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[patchwork-b...@kernel.org]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <da...@davemloft.net>:

On Thu, 2 Dec 2021 15:37:24 -0800 you wrote:
> From: Eric Dumazet <edum...@google.com>
>
> KMSAN is still not happy [1].
>
> I missed that passive connections do not inherit their
> sk_rx_queue_mapping values from the request socket,
> but instead tcp_child_process() is calling
> sk_mark_napi_id(child, skb)
>

> [...]

Here is the summary with links:
- [net] tcp: fix another uninit-value (sk_rx_queue_mapping)
https://git.kernel.org/netdev/net/c/03cfda4fa6ea

You are awesome, thank you!
--
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