[PATCH 5.15 030/128] inet: fully convert sk->sk_rx_dst to RCU rules

Greg Kroah-Hartman
2021-12-27T15:45:49Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 8f905c0e7354ef261360fb7535ea079b1082c105 ]

syzbot reported various issues around early demux,
one being included in this changelog [1]

sk->sk_rx_dst is using RCU protection without clearly
documenting it.

And following sequences in tcp_v4_do_rcv()/tcp_v6_do_rcv()
are not following standard RCU rules.

[a] dst_release(dst);
[b] sk->sk_rx_dst = NULL;

They look wrong because a delete operation of RCU protected
pointer is supposed to clear the pointer before
the call_rcu()/synchronize_rcu() guarding actual memory freeing.

In some cases indeed, dst could be freed before [b] is done.

We could cheat by clearing sk_rx_dst before calling
dst_release(), but this seems the right time to stick
to standard RCU annotations and debugging facilities.

[1]
BUG: KASAN: use-after-free in dst_check include/net/dst.h:470 [inline]
BUG: KASAN: use-after-free in tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792
Read of size 2 at addr ffff88807f1cb73a by task syz-executor.5/9204

CPU: 0 PID: 9204 Comm: syz-executor.5 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
dst_check include/net/dst.h:470 [inline]
tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792
ip_rcv_finish_core.constprop.0+0x15de/0x1e80 net/ipv4/ip_input.c:340
ip_list_rcv_finish.constprop.0+0x1b2/0x6e0 net/ipv4/ip_input.c:583
ip_sublist_rcv net/ipv4/ip_input.c:609 [inline]
ip_list_rcv+0x34e/0x490 net/ipv4/ip_input.c:644
__netif_receive_skb_list_ptype net/core/dev.c:5508 [inline]
__netif_receive_skb_list_core+0x549/0x8e0 net/core/dev.c:5556
__netif_receive_skb_list net/core/dev.c:5608 [inline]
netif_receive_skb_list_internal+0x75e/0xd80 net/core/dev.c:5699
gro_normal_list net/core/dev.c:5853 [inline]
gro_normal_list net/core/dev.c:5849 [inline]
napi_complete_done+0x1f1/0x880 net/core/dev.c:6590
virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline]
virtnet_poll+0xca2/0x11b0 drivers/net/virtio_net.c:1557
__napi_poll+0xaf/0x440 net/core/dev.c:7023
napi_poll net/core/dev.c:7090 [inline]
net_rx_action+0x801/0xb40 net/core/dev.c:7177
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558
invoke_softirq kernel/softirq.c:432 [inline]
__irq_exit_rcu+0x123/0x180 kernel/softirq.c:637
irq_exit_rcu+0x5/0x20 kernel/softirq.c:649
common_interrupt+0x52/0xc0 arch/x86/kernel/irq.c:240
asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629
RIP: 0033:0x7f5e972bfd57
Code: 39 d1 73 14 0f 1f 80 00 00 00 00 48 8b 50 f8 48 83 e8 08 48 39 ca 77 f3 48 39 c3 73 3e 48 89 13 48 8b 50 f8 48 89 38 49 8b 0e <48> 8b 3e 48 83 c3 08 48 83 c6 08 eb bc 48 39 d1 72 9e 48 39 d0 73
RSP: 002b:00007fff8a413210 EFLAGS: 00000283
RAX: 00007f5e97108990 RBX: 00007f5e97108338 RCX: ffffffff81d3aa45
RDX: ffffffff81d3aa45 RSI: 00007f5e97108340 RDI: ffffffff81d3aa45
RBP: 00007f5e97107eb8 R08: 00007f5e97108d88 R09: 0000000093c2e8d9
R10: 0000000000000000 R11: 0000000000000000 R12: 00007f5e97107eb0
R13: 00007f5e97108338 R14: 00007f5e97107ea8 R15: 0000000000000019
</TASK>

Allocated by task 13:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
__kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:467
kasan_slab_alloc include/linux/kasan.h:259 [inline]
slab_post_alloc_hook mm/slab.h:519 [inline]
slab_alloc_node mm/slub.c:3234 [inline]
slab_alloc mm/slub.c:3242 [inline]
kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3247
dst_alloc+0x146/0x1f0 net/core/dst.c:92
rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1613
ip_route_input_slow+0x1817/0x3a20 net/ipv4/route.c:2340
ip_route_input_rcu net/ipv4/route.c:2470 [inline]
ip_route_input_noref+0x116/0x2a0 net/ipv4/route.c:2415
ip_rcv_finish_core.constprop.0+0x288/0x1e80 net/ipv4/ip_input.c:354
ip_list_rcv_finish.constprop.0+0x1b2/0x6e0 net/ipv4/ip_input.c:583
ip_sublist_rcv net/ipv4/ip_input.c:609 [inline]
ip_list_rcv+0x34e/0x490 net/ipv4/ip_input.c:644
__netif_receive_skb_list_ptype net/core/dev.c:5508 [inline]
__netif_receive_skb_list_core+0x549/0x8e0 net/core/dev.c:5556
__netif_receive_skb_list net/core/dev.c:5608 [inline]
netif_receive_skb_list_internal+0x75e/0xd80 net/core/dev.c:5699
gro_normal_list net/core/dev.c:5853 [inline]
gro_normal_list net/core/dev.c:5849 [inline]
napi_complete_done+0x1f1/0x880 net/core/dev.c:6590
virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline]
virtnet_poll+0xca2/0x11b0 drivers/net/virtio_net.c:1557
__napi_poll+0xaf/0x440 net/core/dev.c:7023
napi_poll net/core/dev.c:7090 [inline]
net_rx_action+0x801/0xb40 net/core/dev.c:7177
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558

Freed by task 13:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xff/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1749
slab_free mm/slub.c:3513 [inline]
kmem_cache_free+0xbd/0x5d0 mm/slub.c:3530
dst_destroy+0x2d6/0x3f0 net/core/dst.c:127
rcu_do_batch kernel/rcu/tree.c:2506 [inline]
rcu_core+0x7ab/0x1470 kernel/rcu/tree.c:2741
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558

Last potentially related work creation:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
__kasan_record_aux_stack+0xf5/0x120 mm/kasan/generic.c:348
__call_rcu kernel/rcu/tree.c:2985 [inline]
call_rcu+0xb1/0x740 kernel/rcu/tree.c:3065
dst_release net/core/dst.c:177 [inline]
dst_release+0x79/0xe0 net/core/dst.c:167
tcp_v4_do_rcv+0x612/0x8d0 net/ipv4/tcp_ipv4.c:1712
sk_backlog_rcv include/net/sock.h:1030 [inline]
__release_sock+0x134/0x3b0 net/core/sock.c:2768
release_sock+0x54/0x1b0 net/core/sock.c:3300
tcp_sendmsg+0x36/0x40 net/ipv4/tcp.c:1441
inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:819
sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:724
sock_write_iter+0x289/0x3c0 net/socket.c:1057
call_write_iter include/linux/fs.h:2162 [inline]
new_sync_write+0x429/0x660 fs/read_write.c:503
vfs_write+0x7cd/0xae0 fs/read_write.c:590
ksys_write+0x1ee/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88807f1cb700
which belongs to the cache ip_dst_cache of size 176
The buggy address is located 58 bytes inside of
176-byte region [ffff88807f1cb700, ffff88807f1cb7b0)
The buggy address belongs to the page:
page:ffffea0001fc72c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7f1cb
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 dead000000000100 dead000000000122 ffff8881413bb780
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_HARDWALL), pid 5, ts 108466983062, free_ts 108048976062
prep_new_page mm/page_alloc.c:2418 [inline]
get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4149
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5369
alloc_pages+0x1a7/0x300 mm/mempolicy.c:2191
alloc_slab_page mm/slub.c:1793 [inline]
allocate_slab mm/slub.c:1930 [inline]
new_slab+0x32d/0x4a0 mm/slub.c:1993
___slab_alloc+0x918/0xfe0 mm/slub.c:3022
__slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3109
slab_alloc_node mm/slub.c:3200 [inline]
slab_alloc mm/slub.c:3242 [inline]
kmem_cache_alloc+0x35c/0x3a0 mm/slub.c:3247
dst_alloc+0x146/0x1f0 net/core/dst.c:92
rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1613
__mkroute_output net/ipv4/route.c:2564 [inline]
ip_route_output_key_hash_rcu+0x921/0x2d00 net/ipv4/route.c:2791
ip_route_output_key_hash+0x18b/0x300 net/ipv4/route.c:2619
__ip_route_output_key include/net/route.h:126 [inline]
ip_route_output_flow+0x23/0x150 net/ipv4/route.c:2850
ip_route_output_key include/net/route.h:142 [inline]
geneve_get_v4_rt+0x3a6/0x830 drivers/net/geneve.c:809
geneve_xmit_skb drivers/net/geneve.c:899 [inline]
geneve_xmit+0xc4a/0x3540 drivers/net/geneve.c:1082
__netdev_start_xmit include/linux/netdevice.h:4994 [inline]
netdev_start_xmit include/linux/netdevice.h:5008 [inline]
xmit_one net/core/dev.c:3590 [inline]
dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3606
__dev_queue_xmit+0x299a/0x3650 net/core/dev.c:4229
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1338 [inline]
free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1389
free_unref_page_prepare mm/page_alloc.c:3309 [inline]
free_unref_page+0x19/0x690 mm/page_alloc.c:3388
qlink_free mm/kasan/quarantine.c:146 [inline]
qlist_free_all+0x5a/0xc0 mm/kasan/quarantine.c:165
kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:272
__kasan_slab_alloc+0xa2/0xc0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:259 [inline]
slab_post_alloc_hook mm/slab.h:519 [inline]
slab_alloc_node mm/slub.c:3234 [inline]
kmem_cache_alloc_node+0x255/0x3f0 mm/slub.c:3270
__alloc_skb+0x215/0x340 net/core/skbuff.c:414
alloc_skb include/linux/skbuff.h:1126 [inline]
alloc_skb_with_frags+0x93/0x620 net/core/skbuff.c:6078
sock_alloc_send_pskb+0x783/0x910 net/core/sock.c:2575
mld_newpack+0x1df/0x770 net/ipv6/mcast.c:1754
add_grhead+0x265/0x330 net/ipv6/mcast.c:1857
add_grec+0x1053/0x14e0 net/ipv6/mcast.c:1995
mld_send_initial_cr.part.0+0xf6/0x230 net/ipv6/mcast.c:2242
mld_send_initial_cr net/ipv6/mcast.c:1232 [inline]
mld_dad_work+0x1d3/0x690 net/ipv6/mcast.c:2268
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298
worker_thread+0x658/0x11f0 kernel/workqueue.c:2445

Memory state around the buggy address:
ffff88807f1cb600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807f1cb680: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
>ffff88807f1cb700: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807f1cb780: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
ffff88807f1cb800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Fixes: 41063e9dd119 ("ipv4: Early TCP socket demux.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20211220143330.680945-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/sock.h | 2 +-
net/ipv4/af_inet.c | 2 +-
net/ipv4/tcp.c | 3 +--
net/ipv4/tcp_input.c | 2 +-
net/ipv4/tcp_ipv4.c | 11 +++++++----
net/ipv4/udp.c | 6 +++---
net/ipv6/tcp_ipv6.c | 11 +++++++----
net/ipv6/udp.c | 4 ++--
8 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 796f859c69dd7..dfb92f91d5be5 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -432,7 +432,7 @@ struct sock {
#ifdef CONFIG_XFRM
struct xfrm_policy __rcu *sk_policy[2];
#endif
- struct dst_entry *sk_rx_dst;
+ struct dst_entry __rcu *sk_rx_dst;
int sk_rx_dst_ifindex;
u32 sk_rx_dst_cookie;

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 64062b7ce61df..3a9422a5873eb 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -158,7 +158,7 @@ void inet_sock_destruct(struct sock *sk)

kfree(rcu_dereference_protected(inet->inet_opt, 1));
dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1));
- dst_release(sk->sk_rx_dst);
+ dst_release(rcu_dereference_protected(sk->sk_rx_dst, 1));
sk_refcnt_debug_dec(sk);
}
EXPORT_SYMBOL(inet_sock_destruct);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 844c6e5a82891..f48f1059b31a6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3039,8 +3039,7 @@ int tcp_disconnect(struct sock *sk, int flags)
icsk->icsk_ack.rcv_mss = TCP_MIN_MSS;
memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
__sk_dst_reset(sk);
- dst_release(sk->sk_rx_dst);
- sk->sk_rx_dst = NULL;
+ dst_release(xchg((__force struct dst_entry **)&sk->sk_rx_dst, NULL));
tcp_saved_syn_free(tp);
tp->compressed_ack = 0;
tp->segs_in = 0;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 141e85e6422b1..f3b6239674361 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5770,7 +5770,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
trace_tcp_probe(sk, skb);

tcp_mstamp_refresh(tp);
- if (unlikely(!sk->sk_rx_dst))
+ if (unlikely(!rcu_access_pointer(sk->sk_rx_dst)))
inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
/*
* Header prediction.
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index f6838eec6ef73..0fe9461647da5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1698,7 +1698,10 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
struct sock *rsk;

if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
- struct dst_entry *dst = sk->sk_rx_dst;
+ struct dst_entry *dst;
+
+ dst = rcu_dereference_protected(sk->sk_rx_dst,
+ lockdep_sock_is_held(sk));

sock_rps_save_rxhash(sk, skb);
sk_mark_napi_id(sk, skb);
@@ -1706,8 +1709,8 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
if (sk->sk_rx_dst_ifindex != skb->skb_iif ||
!INDIRECT_CALL_1(dst->ops->check, ipv4_dst_check,
dst, 0)) {
+ RCU_INIT_POINTER(sk->sk_rx_dst, NULL);
dst_release(dst);
- sk->sk_rx_dst = NULL;
}
}
tcp_rcv_established(sk, skb);
@@ -1783,7 +1786,7 @@ int tcp_v4_early_demux(struct sk_buff *skb)
skb->sk = sk;
skb->destructor = sock_edemux;
if (sk_fullsock(sk)) {
- struct dst_entry *dst = READ_ONCE(sk->sk_rx_dst);
+ struct dst_entry *dst = rcu_dereference(sk->sk_rx_dst);

if (dst)
dst = dst_check(dst, 0);
@@ -2200,7 +2203,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
struct dst_entry *dst = skb_dst(skb);

if (dst && dst_hold_safe(dst)) {
- sk->sk_rx_dst = dst;
+ rcu_assign_pointer(sk->sk_rx_dst, dst);
sk->sk_rx_dst_ifindex = skb->skb_iif;
}
}
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 3f6823bdd31e5..be07e3d2b77bc 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2251,7 +2251,7 @@ bool udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
struct dst_entry *old;

if (dst_hold_safe(dst)) {
- old = xchg(&sk->sk_rx_dst, dst);
+ old = xchg((__force struct dst_entry **)&sk->sk_rx_dst, dst);
dst_release(old);
return old != dst;
}
@@ -2441,7 +2441,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
struct dst_entry *dst = skb_dst(skb);
int ret;

- if (unlikely(sk->sk_rx_dst != dst))
+ if (unlikely(rcu_dereference(sk->sk_rx_dst) != dst))
udp_sk_rx_dst_set(sk, dst);

ret = udp_unicast_rcv_skb(sk, skb, uh);
@@ -2600,7 +2600,7 @@ int udp_v4_early_demux(struct sk_buff *skb)

skb->sk = sk;
skb->destructor = sock_efree;
- dst = READ_ONCE(sk->sk_rx_dst);
+ dst = rcu_dereference(sk->sk_rx_dst);

if (dst)
dst = dst_check(dst, 0);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 42eafe35415d1..8eedf59e9cf25 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -107,7 +107,7 @@ static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
if (dst && dst_hold_safe(dst)) {
const struct rt6_info *rt = (const struct rt6_info *)dst;

- sk->sk_rx_dst = dst;
+ rcu_assign_pointer(sk->sk_rx_dst, dst);
sk->sk_rx_dst_ifindex = skb->skb_iif;
sk->sk_rx_dst_cookie = rt6_get_cookie(rt);
}
@@ -1504,7 +1504,10 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
opt_skb = skb_clone(skb, sk_gfp_mask(sk, GFP_ATOMIC));

if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
- struct dst_entry *dst = sk->sk_rx_dst;
+ struct dst_entry *dst;
+
+ dst = rcu_dereference_protected(sk->sk_rx_dst,
+ lockdep_sock_is_held(sk));

sock_rps_save_rxhash(sk, skb);
sk_mark_napi_id(sk, skb);
@@ -1512,8 +1515,8 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
if (sk->sk_rx_dst_ifindex != skb->skb_iif ||
INDIRECT_CALL_1(dst->ops->check, ip6_dst_check,
dst, sk->sk_rx_dst_cookie) == NULL) {
+ RCU_INIT_POINTER(sk->sk_rx_dst, NULL);
dst_release(dst);
- sk->sk_rx_dst = NULL;
}
}

@@ -1875,7 +1878,7 @@ INDIRECT_CALLABLE_SCOPE void tcp_v6_early_demux(struct sk_buff *skb)
skb->sk = sk;
skb->destructor = sock_edemux;
if (sk_fullsock(sk)) {
- struct dst_entry *dst = READ_ONCE(sk->sk_rx_dst);
+ struct dst_entry *dst = rcu_dereference(sk->sk_rx_dst);

if (dst)
dst = dst_check(dst, sk->sk_rx_dst_cookie);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 12c12619ee357..7bee95d8d2df0 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -956,7 +956,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
struct dst_entry *dst = skb_dst(skb);
int ret;

- if (unlikely(sk->sk_rx_dst != dst))
+ if (unlikely(rcu_dereference(sk->sk_rx_dst) != dst))
udp6_sk_rx_dst_set(sk, dst);

if (!uh->check && !udp_sk(sk)->no_check6_rx) {
@@ -1070,7 +1070,7 @@ INDIRECT_CALLABLE_SCOPE void udp_v6_early_demux(struct sk_buff *skb)

skb->sk = sk;
skb->destructor = sock_efree;
- dst = READ_ONCE(sk->sk_rx_dst);
+ dst = rcu_dereference(sk->sk_rx_dst);

if (dst)
dst = dst_check(dst, sk->sk_rx_dst_cookie);
--
2.34.1