Subject: WARNING: suspicious RCU usage in ovs_flow_tbl_masks_cache_resize

From: syzbot <[email-masked]>
Date: Wed, 28 Oct 2020 08:33:17 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    6daa1da4 chelsio/chtls: fix memory leaks in CPL handlers
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=10defae4500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=46c6fea3eb827ae1
dashboard link: https://syzkaller.appspot.com/bug?extid=9a8f8bfcc56e8578016c
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15fed5bc500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12afff40500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

netlink: 44 bytes leftover after parsing attributes in process `syz-executor522'.
=============================
WARNING: suspicious RCU usage
5.9.0-syzkaller #0 Not tainted
-----------------------------
net/openvswitch/flow_table.c:393 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-executor522/8493:
 #0: ffffffff8c9af210 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:810

stack backtrace:
CPU: 1 PID: 8493 Comm: syz-executor522 Not tainted 5.9.0-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+0x107/0x163 lib/dump_stack.c:118
 ovs_flow_tbl_masks_cache_resize+0x1bf/0x200 net/openvswitch/flow_table.c:393
 ovs_dp_change+0x231/0x2b0 net/openvswitch/datapath.c:1616
 ovs_dp_cmd_new+0x4c1/0xec0 net/openvswitch/datapath.c:1706
 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:739
 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline]
 genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:800
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:811
 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:2353
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2407
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2440
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x440ad9
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:00007ffff6e416d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440ad9
RDX: 0000000000000000 RSI: 0000000020000500 RDI: 0000000000000003
RBP: 00000000006cb018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004022e0

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