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authorJohn Fastabend <john.fastabend@gmail.com>2017-09-08 14:00:30 -0700
committerDavid S. Miller <davem@davemloft.net>2017-09-08 21:11:00 -0700
commitbbbe211c295ffb309247adb7b871dda60d92d2d5 (patch)
tree7d4b7d13d3455fd2e2288296a775792f04cea3cd /net/core
parent109980b894e9dae66c37c3d804a415aa68b19c7e (diff)
downloadlinux-bbbe211c295ffb309247adb7b871dda60d92d2d5.tar.bz2
net: rcu lock and preempt disable missing around generic xdp
do_xdp_generic must be called inside rcu critical section with preempt disabled to ensure BPF programs are valid and per-cpu variables used for redirect operations are consistent. This patch ensures this is true and fixes the splat below. The netif_receive_skb_internal() code path is now broken into two rcu critical sections. I decided it was better to limit the preempt_enable/disable block to just the xdp static key portion and the fallout is more rcu_read_lock/unlock calls. Seems like the best option to me. [ 607.596901] ============================= [ 607.596906] WARNING: suspicious RCU usage [ 607.596912] 4.13.0-rc4+ #570 Not tainted [ 607.596917] ----------------------------- [ 607.596923] net/core/dev.c:3948 suspicious rcu_dereference_check() usage! [ 607.596927] [ 607.596927] other info that might help us debug this: [ 607.596927] [ 607.596933] [ 607.596933] rcu_scheduler_active = 2, debug_locks = 1 [ 607.596938] 2 locks held by pool/14624: [ 607.596943] #0: (rcu_read_lock_bh){......}, at: [<ffffffff95445ffd>] ip_finish_output2+0x14d/0x890 [ 607.596973] #1: (rcu_read_lock_bh){......}, at: [<ffffffff953c8e3a>] __dev_queue_xmit+0x14a/0xfd0 [ 607.597000] [ 607.597000] stack backtrace: [ 607.597006] CPU: 5 PID: 14624 Comm: pool Not tainted 4.13.0-rc4+ #570 [ 607.597011] Hardware name: Dell Inc. Precision Tower 5810/0HHV7N, BIOS A17 03/01/2017 [ 607.597016] Call Trace: [ 607.597027] dump_stack+0x67/0x92 [ 607.597040] lockdep_rcu_suspicious+0xdd/0x110 [ 607.597054] do_xdp_generic+0x313/0xa50 [ 607.597068] ? time_hardirqs_on+0x5b/0x150 [ 607.597076] ? mark_held_locks+0x6b/0xc0 [ 607.597088] ? netdev_pick_tx+0x150/0x150 [ 607.597117] netif_rx_internal+0x205/0x3f0 [ 607.597127] ? do_xdp_generic+0xa50/0xa50 [ 607.597144] ? lock_downgrade+0x2b0/0x2b0 [ 607.597158] ? __lock_is_held+0x93/0x100 [ 607.597187] netif_rx+0x119/0x190 [ 607.597202] loopback_xmit+0xfd/0x1b0 [ 607.597214] dev_hard_start_xmit+0x127/0x4e0 Fixes: d445516966dc ("net: xdp: support xdp generic on virtual devices") Fixes: b5cdae3291f7 ("net: Generic XDP") Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/dev.c25
1 files changed, 16 insertions, 9 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index 6f845e4fec17..fb766d906148 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3981,8 +3981,13 @@ static int netif_rx_internal(struct sk_buff *skb)
trace_netif_rx(skb);
if (static_key_false(&generic_xdp_needed)) {
- int ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog),
- skb);
+ int ret;
+
+ preempt_disable();
+ rcu_read_lock();
+ ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog), skb);
+ rcu_read_unlock();
+ preempt_enable();
/* Consider XDP consuming the packet a success from
* the netdev point of view we do not want to count
@@ -4500,18 +4505,20 @@ static int netif_receive_skb_internal(struct sk_buff *skb)
if (skb_defer_rx_timestamp(skb))
return NET_RX_SUCCESS;
- rcu_read_lock();
-
if (static_key_false(&generic_xdp_needed)) {
- int ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog),
- skb);
+ int ret;
- if (ret != XDP_PASS) {
- rcu_read_unlock();
+ preempt_disable();
+ rcu_read_lock();
+ ret = do_xdp_generic(rcu_dereference(skb->dev->xdp_prog), skb);
+ rcu_read_unlock();
+ preempt_enable();
+
+ if (ret != XDP_PASS)
return NET_RX_DROP;
- }
}
+ rcu_read_lock();
#ifdef CONFIG_RPS
if (static_key_false(&rps_needed)) {
struct rps_dev_flow voidflow, *rflow = &voidflow;