net/sched: Add xmit_recursion level in sch_direct_xmit()

packet from PF_PACKET socket ontop of an IPv6-backed ipvlan device will hit
WARN_ON_ONCE() in sk_mc_loop() through sch_direct_xmit() path while ipvlan
device has qdisc queue.

WARNING: CPU: 2 PID: 0 at net/core/sock.c:775 sk_mc_loop+0x2d/0x70
Modules linked in: sch_netem ipvlan rfkill cirrus drm_shmem_helper sg drm_kms_helper
CPU: 2 PID: 0 Comm: swapper/2 Kdump: loaded Not tainted 6.9.0+ torvalds#279
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:sk_mc_loop+0x2d/0x70
Code: fa 0f 1f 44 00 00 65 0f b7 15 f7 96 a3 4f 31 c0 66 85 d2 75 26 48 85 ff 74 1c
RSP: 0018:ffffa9584015cd78 EFLAGS: 00010212
RAX: 0000000000000011 RBX: ffff91e585793e00 RCX: 0000000002c6a001
RDX: 0000000000000000 RSI: 0000000000000040 RDI: ffff91e589c0f000
RBP: ffff91e5855bd100 R08: 0000000000000000 R09: 3d00545216f43d00
R10: ffff91e584fdcc50 R11: 00000060dd8616f4 R12: ffff91e58132d000
R13: ffff91e584fdcc68 R14: ffff91e5869ce800 R15: ffff91e589c0f000
FS:  0000000000000000(0000) GS:ffff91e898100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f788f7c44c0 CR3: 0000000008e1a000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 ? __warn+0x83/0x130
 ? sk_mc_loop+0x2d/0x70
 ? report_bug+0x18e/0x1a0
 ? handle_bug+0x3c/0x70
 ? exc_invalid_op+0x18/0x70
 ? asm_exc_invalid_op+0x1a/0x20
 ? sk_mc_loop+0x2d/0x70
 ip6_finish_output2+0x31e/0x590
 ? nf_hook_slow+0x43/0xf0
 ip6_finish_output+0x1f8/0x320
 ? __pfx_ip6_finish_output+0x10/0x10
 ipvlan_xmit_mode_l3+0x22a/0x2a0 [ipvlan]
 ipvlan_start_xmit+0x17/0x50 [ipvlan]
 dev_hard_start_xmit+0x8c/0x1d0
 sch_direct_xmit+0xa2/0x390
 __qdisc_run+0x66/0xd0
 net_tx_action+0x1ca/0x270
 handle_softirqs+0xd6/0x2b0
 __irq_exit_rcu+0x9b/0xc0
 sysvec_apic_timer_interrupt+0x75/0x90
 </IRQ>

Fixes: f60e599 ("ipv6: protect skb->sk accesses from recursive dereference inside the stack")
Signed-off-by: Yue Haibing <[email protected]>

Author: Yue Haibing

include/linux/netdevice.h

@@ -3261,6 +3261,23 @@ static inline int dev_recursion_level(void)
 	return this_cpu_read(softnet_data.xmit.recursion);
 }
 
+#define XMIT_RECURSION_LIMIT	8
+static inline bool dev_xmit_recursion(void)
+{
+	return unlikely(__this_cpu_read(softnet_data.xmit.recursion) >
+			XMIT_RECURSION_LIMIT);
+}
+
+static inline void dev_xmit_recursion_inc(void)
+{
+	__this_cpu_inc(softnet_data.xmit.recursion);
+}
+
+static inline void dev_xmit_recursion_dec(void)
+{
+	__this_cpu_dec(softnet_data.xmit.recursion);
+}
+
 void __netif_schedule(struct Qdisc *q);
 void netif_schedule_queue(struct netdev_queue *txq);
 

net/core/dev.h

@@ -149,21 +149,4 @@ static inline void xdp_do_check_flushed(struct napi_struct *napi) { }
 struct napi_struct *napi_by_id(unsigned int napi_id);
 void kick_defer_list_purge(struct softnet_data *sd, unsigned int cpu);
 
-#define XMIT_RECURSION_LIMIT	8
-static inline bool dev_xmit_recursion(void)
-{
-	return unlikely(__this_cpu_read(softnet_data.xmit.recursion) >
-			XMIT_RECURSION_LIMIT);
-}
-
-static inline void dev_xmit_recursion_inc(void)
-{
-	__this_cpu_inc(softnet_data.xmit.recursion);
-}
-
-static inline void dev_xmit_recursion_dec(void)
-{
-	__this_cpu_dec(softnet_data.xmit.recursion);
-}
-
 #endif

net/sched/sch_generic.c

@@ -339,11 +339,13 @@ bool sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
 
 	if (likely(skb)) {
 		HARD_TX_LOCK(dev, txq, smp_processor_id());
-		if (!netif_xmit_frozen_or_stopped(txq))
+		if (!netif_xmit_frozen_or_stopped(txq)) {
+			dev_xmit_recursion_inc();
 			skb = dev_hard_start_xmit(skb, dev, txq, &ret);
-		else
+			dev_xmit_recursion_dec();
+		} else {
 			qdisc_maybe_clear_missed(q, txq);
-
+		}
 		HARD_TX_UNLOCK(dev, txq);
 	} else {
 		if (root_lock)