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WARNING: suspicious RCU usage in ovs_flow_tbl_masks_cache_size

Status: fixed on 2020/09/16 22:51
Subsystems: openvswitch
[Documentation on labels]
Reported-by: syzbot+f612c02823acb02ff9bc@syzkaller.appspotmail.com
Fix commit: fea07a487c6d net: openvswitch: silence suspicious RCU usage warning
First crash: 1355d, last: 1352d
Cause bisection: introduced by (bisect log) :
commit 9bf24f594c6acf676fb8c229f152c21bfb915ddb
Author: Eelco Chaudron <echaudro@redhat.com>
Date: Fri Jul 31 12:21:34 2020 +0000

  net: openvswitch: make masks cache size configurable

Crash: WARNING: suspicious RCU usage in ovs_flow_tbl_masks_cache_size (log)
Repro: C syz .config
  
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] net: openvswitch: silence suspicious RCU usage warning 4 (4) 2020/08/05 19:21
WARNING: suspicious RCU usage in ovs_flow_tbl_masks_cache_size 0 (2) 2020/08/05 00:24
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2020/08/04 17:22 0m pabeni@redhat.com patch net-next-old error OK

Sample crash report:
netlink: 'syz-executor988': attribute type 2 has an invalid length.
device  entered promiscuous mode
=============================
WARNING: suspicious RCU usage
5.8.0-rc7-syzkaller #0 Not tainted
-----------------------------
net/openvswitch/flow_table.c:940 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
2 locks held by syz-executor988/6892:
 #0: ffffffff8a832390 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:741
 #1: ffffffff8aa792e8 (ovs_mutex){+.+.}-{3:3}, at: ovs_lock net/openvswitch/datapath.c:105 [inline]
 #1: ffffffff8aa792e8 (ovs_mutex){+.+.}-{3:3}, at: ovs_dp_cmd_new+0x4db/0xea0 net/openvswitch/datapath.c:1707

stack backtrace:
CPU: 1 PID: 6892 Comm: syz-executor988 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_masks_cache_size+0xc3/0xe0 net/openvswitch/flow_table.c:940
 ovs_dp_cmd_fill_info+0x4e4/0x880 net/openvswitch/datapath.c:1539
 ovs_dp_cmd_new+0x584/0xea0 net/openvswitch/datapath.c:1728
 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:00007ffd1247e9a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402d9
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8

Crashes (4093):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/08/05 12:13 bpf-next da7955405fb2 b7129355 .config console log report syz C ci-upstream-bpf-next-kasan-gce
2020/08/04 07:12 net-next-old 2f631133c40c 196277c4 .config console log report syz C ci-upstream-net-kasan-gce
2020/08/06 22:01 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 21:49 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 21:38 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 21:27 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 21:12 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 21:03 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 20:51 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 20:38 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 20:27 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 20:17 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 20:06 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 19:55 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 19:45 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 19:34 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 19:21 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 19:08 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 18:54 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 18:43 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 18:30 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 18:18 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 18:08 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 17:58 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 17:46 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 17:32 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 17:19 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 17:07 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 16:52 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 16:42 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 16:31 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 16:21 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 16:09 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 15:56 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 15:45 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 15:32 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 15:15 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 14:59 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 14:47 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 14:33 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 14:14 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 13:52 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/06 13:31 bpf-next da7955405fb2 1f122f88 .config console log report ci-upstream-bpf-next-kasan-gce
2020/08/05 22:34 net-next-old 4c900a6b4e05 b7129355 .config console log report ci-upstream-net-kasan-gce
2020/08/04 06:06 net-next-old 2f631133c40c 196277c4 .config console log report ci-upstream-net-kasan-gce
* Struck through repros no longer work on HEAD.