WARNING: suspicious RCU usage in ovs_flow_tbl_destroy

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    2f631133 net: Pass NULL to skb_network_protocol() when we ..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12daae2a900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=91a13b78c7dc258d
dashboard link: https://syzkaller.appspot.com/bug?extid=c0eb9e7cdde04e4eb4be
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=172cd3d4900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11fbd342900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c0eb9e7cdde04e4eb4be@xxxxxxxxxxxxxxxxxxxxxxxxx

netlink: 'syz-executor399': attribute type 2 has an invalid length.
=============================
WARNING: suspicious RCU usage
5.8.0-rc7-syzkaller #0 Not tainted
-----------------------------
net/openvswitch/flow_table.c:521 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor399/6802:
 #0: ffffffff8a8319b0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:741

stack backtrace:
CPU: 0 PID: 6802 Comm: syz-executor399 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 ovs_flow_tbl_destroy+0x1d6/0x210 net/openvswitch/flow_table.c:521
 ovs_dp_cmd_new+0x8ca/0xea0 net/openvswitch/datapath.c:1747
 genl_family_rcv_msg_doit net/netlink/genetlink.c:669 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:714 [inline]
 genl_rcv_msg+0x61d/0x980 net/netlink/genetlink.c:731
 netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:742
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2359
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2413
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2446
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4402d9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdfda722f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401ae0
R13: 0000000000401b70 R14: 0000000000000000 R15: 0000000000000000

=============================
WARNING: suspicious RCU usage
5.8.0-rc7-syzkaller #0 Not tainted
-----------------------------
net/openvswitch/flow_table.c:522 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor399/6802:
 #0: ffffffff8a8319b0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:741

stack backtrace:
CPU: 0 PID: 6802 Comm: syz-executor399 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 ovs_flow_tbl_destroy+0x190/0x210 net/openvswitch/flow_table.c:522
 ovs_dp_cmd_new+0x8ca/0xea0 net/openvswitch/datapath.c:1747
 genl_family_rcv_msg_doit net/netlink/genetlink.c:669 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:714 [inline]
 genl_rcv_msg+0x61d/0x980 net/netlink/genetlink.c:731
 netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:742
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2359
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2413
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2446
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4402d9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdfda722f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000400


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