[PATCH 5.8 012/633] net: sched: Fix suspicious RCU usage while accessing tcf_tunnel_info

Greg Kroah-Hartman
2020-10-27T14:52:14Z

From: Leon Romanovsky <leonro@nvidia.com>

[ Upstream commit d086a1c65aabb5a4e1edc580ca583e2964c62b44 ]

The access of tcf_tunnel_info() produces the following splat, so fix it
by dereferencing the tcf_tunnel_key_params pointer with marker that
internal tcfa_liock is held.

=============================
WARNING: suspicious RCU usage
5.9.0+ #1 Not tainted
-----------------------------
include/net/tc_act/tc_tunnel_key.h:59 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by tc/34839:
#0: ffff88828572c2a0 (&p->tcfa_lock){+...}-{2:2}, at: tc_setup_flow_action+0xb3/0x48b5
stack backtrace:
CPU: 1 PID: 34839 Comm: tc Not tainted 5.9.0+ #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
Call Trace:
dump_stack+0x9a/0xd0
tc_setup_flow_action+0x14cb/0x48b5
fl_hw_replace_filter+0x347/0x690 [cls_flower]
fl_change+0x2bad/0x4875 [cls_flower]
tc_new_tfilter+0xf6f/0x1ba0
rtnetlink_rcv_msg+0x5f2/0x870
netlink_rcv_skb+0x124/0x350
netlink_unicast+0x433/0x700
netlink_sendmsg+0x6f1/0xbd0
sock_sendmsg+0xb0/0xe0
____sys_sendmsg+0x4fa/0x6d0
___sys_sendmsg+0x12e/0x1b0
__sys_sendmsg+0xa4/0x120
do_syscall_64+0x2d/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f1f8cd4fe57
Code: 0c 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 89 74 24 10
RSP: 002b:00007ffdc1e193b8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1f8cd4fe57
RDX: 0000000000000000 RSI: 00007ffdc1e19420 RDI: 0000000000000003
RBP: 000000005f85aafa R08: 0000000000000001 R09: 00007ffdc1e1936c
R10: 000000000040522d R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 00007ffdc1e1d6f0 R15: 0000000000482420

Fixes: 3ebaf6da0716 ("net: sched: Do not assume RTNL is held in tunnel key action helpers")
Fixes: 7a47281439ba ("net: sched: lock action when translating it to flow_action infra")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/tc_act/tc_tunnel_key.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/include/net/tc_act/tc_tunnel_key.h
+++ b/include/net/tc_act/tc_tunnel_key.h
@@ -56,7 +56,10 @@ static inline struct ip_tunnel_info *tcf
{
#ifdef CONFIG_NET_CLS_ACT
struct tcf_tunnel_key *t = to_tunnel_key(a);
- struct tcf_tunnel_key_params *params = rtnl_dereference(t->params);
+ struct tcf_tunnel_key_params *params;
+
+ params = rcu_dereference_protected(t->params,
+ lockdep_is_held(&a->tcfa_lock));

return &params->tcft_enc_metadata->u.tun_info;
#else