This is a note to let you know that I've just added the patch titled
net: do not process device backlog during unregistration
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-do-not-process-device-backlog-during-unregistration.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Sat Sep 26 11:19:08 PDT 2015
From: Julian Anastasov <ja@xxxxxx>
Date: Thu, 9 Jul 2015 09:59:09 +0300
Subject: net: do not process device backlog during unregistration
From: Julian Anastasov <ja@xxxxxx>
[ Upstream commit e9e4dd3267d0c5234c5c0f47440456b10875dec9 ]
commit 381c759d9916 ("ipv4: Avoid crashing in ip_error")
fixes a problem where processed packet comes from device
with destroyed inetdev (dev->ip_ptr). This is not expected
because inetdev_destroy is called in NETDEV_UNREGISTER
phase and packets should not be processed after
dev_close_many() and synchronize_net(). Above fix is still
required because inetdev_destroy can be called for other
reasons. But it shows the real problem: backlog can keep
packets for long time and they do not hold reference to
device. Such packets are then delivered to upper levels
at the same time when device is unregistered.
Calling flush_backlog after NETDEV_UNREGISTER_FINAL still
accounts all packets from backlog but before that some packets
continue to be delivered to upper levels long after the
synchronize_net call which is supposed to wait the last
ones. Also, as Eric pointed out, processed packets, mostly
from other devices, can continue to add new packets to backlog.
Fix the problem by moving flush_backlog early, after the
device driver is stopped and before the synchronize_net() call.
Then use netif_running check to make sure we do not add more
packets to backlog. We have to do it in enqueue_to_backlog
context when the local IRQ is disabled. As result, after the
flush_backlog and synchronize_net sequence all packets
should be accounted.
Thanks to Eric W. Biederman for the test script and his
valuable feedback!
Reported-by: Vittorio Gambaletta <linuxbugs@xxxxxxxxxxx>
Fixes: 6e583ce5242f ("net: eliminate refcounting in backlog queue")
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Julian Anastasov <ja@xxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/core/dev.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3214,6 +3214,8 @@ static int enqueue_to_backlog(struct sk_
local_irq_save(flags);
rps_lock(sd);
+ if (!netif_running(skb->dev))
+ goto drop;
qlen = skb_queue_len(&sd->input_pkt_queue);
if (qlen <= netdev_max_backlog && !skb_flow_limit(skb, qlen)) {
if (skb_queue_len(&sd->input_pkt_queue)) {
@@ -3235,6 +3237,7 @@ enqueue:
goto enqueue;
}
+drop:
sd->dropped++;
rps_unlock(sd);
@@ -5694,6 +5697,7 @@ static void rollback_registered_many(str
unlist_netdevice(dev);
dev->reg_state = NETREG_UNREGISTERING;
+ on_each_cpu(flush_backlog, dev, 1);
}
synchronize_net();
@@ -6310,8 +6314,6 @@ void netdev_run_todo(void)
dev->reg_state = NETREG_UNREGISTERED;
- on_each_cpu(flush_backlog, dev, 1);
-
netdev_wait_allrefs(dev);
/* paranoia */
Patches currently in stable-queue which might be from ja@xxxxxx are
queue-3.14/net-call-rcu_read_lock-early-in-process_backlog.patch
queue-3.14/net-do-not-process-device-backlog-during-unregistration.patch
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