net: use a work queue to defer net_disable_timestamp() work

Eric Dumazet · davem330 · commit 5fa8bbda38c6 · 2017-02-03T16:11:07.000-05:00
Dmitry reported a warning [1] showing that we were calling net_disable_timestamp() -> static_key_slow_dec() from a non process context. Grabbing a mutex while holding a spinlock or rcu_read_lock() is not allowed. As Cong suggested, we now use a work queue. It is possible netstamp_clear() exits while netstamp_needed_deferred is not zero, but it is probably not worth trying to do better than that. netstamp_needed_deferred atomic tracks the exact number of deferred decrements. [1] [ INFO: suspicious RCU usage. ] 4.10.0-rc5+ torvalds#192 Not tainted ------------------------------- ./include/linux/rcupdate.h:561 Illegal context switch in RCU read-side critical section! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 0 2 locks held by syz-executor14/23111: #0: (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83a35c35>] lock_sock include/net/sock.h:1454 [inline] #0: (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83a35c35>] rawv6_sendmsg+0x1e65/0x3ec0 net/ipv6/raw.c:919 #1: (rcu_read_lock){......}, at: [<ffffffff83ae2678>] nf_hook include/linux/netfilter.h:201 [inline] #1: (rcu_read_lock){......}, at: [<ffffffff83ae2678>] __ip6_local_out+0x258/0x840 net/ipv6/output_core.c:160 stack backtrace: CPU: 2 PID: 23111 Comm: syz-executor14 Not tainted 4.10.0-rc5+ torvalds#192 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:15 [inline] dump_stack+0x2ee/0x3ef lib/dump_stack.c:51 lockdep_rcu_suspicious+0x139/0x180 kernel/locking/lockdep.c:4452 rcu_preempt_sleep_check include/linux/rcupdate.h:560 [inline] ___might_sleep+0x560/0x650 kernel/sched/core.c:7748 __might_sleep+0x95/0x1a0 kernel/sched/core.c:7739 mutex_lock_nested+0x24f/0x1730 kernel/locking/mutex.c:752 atomic_dec_and_mutex_lock+0x119/0x160 kernel/locking/mutex.c:1060 __static_key_slow_dec+0x7a/0x1e0 kernel/jump_label.c:149 static_key_slow_dec+0x51/0x90 kernel/jump_label.c:174 net_disable_timestamp+0x3b/0x50 net/core/dev.c:1728 sock_disable_timestamp+0x98/0xc0 net/core/sock.c:403 __sk_destruct+0x27d/0x6b0 net/core/sock.c:1441 sk_destruct+0x47/0x80 net/core/sock.c:1460 __sk_free+0x57/0x230 net/core/sock.c:1468 sock_wfree+0xae/0x120 net/core/sock.c:1645 skb_release_head_state+0xfc/0x200 net/core/skbuff.c:655 skb_release_all+0x15/0x60 net/core/skbuff.c:668 __kfree_skb+0x15/0x20 net/core/skbuff.c:684 kfree_skb+0x16e/0x4c0 net/core/skbuff.c:705 inet_frag_destroy+0x121/0x290 net/ipv4/inet_fragment.c:304 inet_frag_put include/net/inet_frag.h:133 [inline] nf_ct_frag6_gather+0x1106/0x3840 net/ipv6/netfilter/nf_conntrack_reasm.c:617 ipv6_defrag+0x1be/0x2b0 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:68 nf_hook_entry_hookfn include/linux/netfilter.h:102 [inline] nf_hook_slow+0xc3/0x290 net/netfilter/core.c:310 nf_hook include/linux/netfilter.h:212 [inline] __ip6_local_out+0x489/0x840 net/ipv6/output_core.c:160 ip6_local_out+0x2d/0x170 net/ipv6/output_core.c:170 ip6_send_skb+0xa1/0x340 net/ipv6/ip6_output.c:1722 ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1742 rawv6_push_pending_frames net/ipv6/raw.c:613 [inline] rawv6_sendmsg+0x2d1a/0x3ec0 net/ipv6/raw.c:927 inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:744 sock_sendmsg_nosec net/socket.c:635 [inline] sock_sendmsg+0xca/0x110 net/socket.c:645 sock_write_iter+0x326/0x600 net/socket.c:848 do_iter_readv_writev+0x2e3/0x5b0 fs/read_write.c:695 do_readv_writev+0x42c/0x9b0 fs/read_write.c:872 vfs_writev+0x87/0xc0 fs/read_write.c:911 do_writev+0x110/0x2c0 fs/read_write.c:944 SYSC_writev fs/read_write.c:1017 [inline] SyS_writev+0x27/0x30 fs/read_write.c:1014 entry_SYSCALL_64_fastpath+0x1f/0xc2 RIP: 0033:0x445559 RSP: 002b:00007f6f46fceb58 EFLAGS: 00000292 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000445559 RDX: 0000000000000001 RSI: 0000000020f1eff0 RDI: 0000000000000005 RBP: 00000000006e19c0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000700000 R13: 0000000020f59000 R14: 0000000000000015 R15: 0000000000020400 BUG: sleeping function called from invalid context at kernel/locking/mutex.c:752 in_atomic(): 1, irqs_disabled(): 0, pid: 23111, name: syz-executor14 INFO: lockdep is turned off. CPU: 2 PID: 23111 Comm: syz-executor14 Not tainted 4.10.0-rc5+ torvalds#192 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:15 [inline] dump_stack+0x2ee/0x3ef lib/dump_stack.c:51 ___might_sleep+0x47e/0x650 kernel/sched/core.c:7780 __might_sleep+0x95/0x1a0 kernel/sched/core.c:7739 mutex_lock_nested+0x24f/0x1730 kernel/locking/mutex.c:752 atomic_dec_and_mutex_lock+0x119/0x160 kernel/locking/mutex.c:1060 __static_key_slow_dec+0x7a/0x1e0 kernel/jump_label.c:149 static_key_slow_dec+0x51/0x90 kernel/jump_label.c:174 net_disable_timestamp+0x3b/0x50 net/core/dev.c:1728 sock_disable_timestamp+0x98/0xc0 net/core/sock.c:403 __sk_destruct+0x27d/0x6b0 net/core/sock.c:1441 sk_destruct+0x47/0x80 net/core/sock.c:1460 __sk_free+0x57/0x230 net/core/sock.c:1468 sock_wfree+0xae/0x120 net/core/sock.c:1645 skb_release_head_state+0xfc/0x200 net/core/skbuff.c:655 skb_release_all+0x15/0x60 net/core/skbuff.c:668 __kfree_skb+0x15/0x20 net/core/skbuff.c:684 kfree_skb+0x16e/0x4c0 net/core/skbuff.c:705 inet_frag_destroy+0x121/0x290 net/ipv4/inet_fragment.c:304 inet_frag_put include/net/inet_frag.h:133 [inline] nf_ct_frag6_gather+0x1106/0x3840 net/ipv6/netfilter/nf_conntrack_reasm.c:617 ipv6_defrag+0x1be/0x2b0 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:68 nf_hook_entry_hookfn include/linux/netfilter.h:102 [inline] nf_hook_slow+0xc3/0x290 net/netfilter/core.c:310 nf_hook include/linux/netfilter.h:212 [inline] __ip6_local_out+0x489/0x840 net/ipv6/output_core.c:160 ip6_local_out+0x2d/0x170 net/ipv6/output_core.c:170 ip6_send_skb+0xa1/0x340 net/ipv6/ip6_output.c:1722 ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1742 rawv6_push_pending_frames net/ipv6/raw.c:613 [inline] rawv6_sendmsg+0x2d1a/0x3ec0 net/ipv6/raw.c:927 inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:744 sock_sendmsg_nosec net/socket.c:635 [inline] sock_sendmsg+0xca/0x110 net/socket.c:645 sock_write_iter+0x326/0x600 net/socket.c:848 do_iter_readv_writev+0x2e3/0x5b0 fs/read_write.c:695 do_readv_writev+0x42c/0x9b0 fs/read_write.c:872 vfs_writev+0x87/0xc0 fs/read_write.c:911 do_writev+0x110/0x2c0 fs/read_write.c:944 SYSC_writev fs/read_write.c:1017 [inline] SyS_writev+0x27/0x30 fs/read_write.c:1014 entry_SYSCALL_64_fastpath+0x1f/0xc2 RIP: 0033:0x445559 Fixes: b90e579 ("net: dont call jump_label_dec from irq context") Suggested-by: Cong Wang <xiyou.wangcong@gmail.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
@@ -1695,37 +1695,32 @@ EXPORT_SYMBOL_GPL(net_dec_egress_queue);
 
 static struct static_key netstamp_needed __read_mostly;
 #ifdef HAVE_JUMP_LABEL
-/* We are not allowed to call static_key_slow_dec() from irq context
- * If net_disable_timestamp() is called from irq context, defer the
- * static_key_slow_dec() calls.
- */
 static atomic_t netstamp_needed_deferred;
-#endif
-
-void net_enable_timestamp(void)
+static void netstamp_clear(struct work_struct *work)
 {
-#ifdef HAVE_JUMP_LABEL
 	int deferred = atomic_xchg(&netstamp_needed_deferred, 0);
 
-	if (deferred) {
-		while (--deferred)
-			static_key_slow_dec(&netstamp_needed);
-		return;
-	}
+	while (deferred--)
+		static_key_slow_dec(&netstamp_needed);
+}
+static DECLARE_WORK(netstamp_work, netstamp_clear);
 #endif
+
+void net_enable_timestamp(void)
+{
 	static_key_slow_inc(&netstamp_needed);
 }
 EXPORT_SYMBOL(net_enable_timestamp);
 
 void net_disable_timestamp(void)
 {
 #ifdef HAVE_JUMP_LABEL
-	if (in_interrupt()) {
-		atomic_inc(&netstamp_needed_deferred);
-		return;
-	}
-#endif
+	/* net_disable_timestamp() can be called from non process context */
+	atomic_inc(&netstamp_needed_deferred);
+	schedule_work(&netstamp_work);
+#else
 	static_key_slow_dec(&netstamp_needed);
+#endif
 }
 EXPORT_SYMBOL(net_disable_timestamp);
 
