This is a note to let you know that I've just added the patch titled
xen-netfront: Fix NULL sring after live migration
to the 5.4-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:
xen-netfront-fix-null-sring-after-live-migration.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit a93e84abca951789f99b176535218d5e92b959fc
Author: Lin Liu <lin.liu@xxxxxxxxxx>
Date: Fri Dec 2 08:52:48 2022 +0000
xen-netfront: Fix NULL sring after live migration
[ Upstream commit d50b7914fae04d840ce36491d22133070b18cca9 ]
A NAPI is setup for each network sring to poll data to kernel
The sring with source host is destroyed before live migration and
new sring with target host is setup after live migration.
The NAPI for the old sring is not deleted until setup new sring
with target host after migration. With busy_poll/busy_read enabled,
the NAPI can be polled before got deleted when resume VM.
BUG: unable to handle kernel NULL pointer dereference at
0000000000000008
IP: xennet_poll+0xae/0xd20
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
Call Trace:
finish_task_switch+0x71/0x230
timerqueue_del+0x1d/0x40
hrtimer_try_to_cancel+0xb5/0x110
xennet_alloc_rx_buffers+0x2a0/0x2a0
napi_busy_loop+0xdb/0x270
sock_poll+0x87/0x90
do_sys_poll+0x26f/0x580
tracing_map_insert+0x1d4/0x2f0
event_hist_trigger+0x14a/0x260
finish_task_switch+0x71/0x230
__schedule+0x256/0x890
recalc_sigpending+0x1b/0x50
xen_sched_clock+0x15/0x20
__rb_reserve_next+0x12d/0x140
ring_buffer_lock_reserve+0x123/0x3d0
event_triggers_call+0x87/0xb0
trace_event_buffer_commit+0x1c4/0x210
xen_clocksource_get_cycles+0x15/0x20
ktime_get_ts64+0x51/0xf0
SyS_ppoll+0x160/0x1a0
SyS_ppoll+0x160/0x1a0
do_syscall_64+0x73/0x130
entry_SYSCALL_64_after_hwframe+0x41/0xa6
...
RIP: xennet_poll+0xae/0xd20 RSP: ffffb4f041933900
CR2: 0000000000000008
---[ end trace f8601785b354351c ]---
xen frontend should remove the NAPIs for the old srings before live
migration as the bond srings are destroyed
There is a tiny window between the srings are set to NULL and
the NAPIs are disabled, It is safe as the NAPI threads are still
frozen at that time
Signed-off-by: Lin Liu <lin.liu@xxxxxxxxxx>
Fixes: 4ec2411980d0 ([NET]: Do not check netif_running() and carrier state in ->poll())
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 810fa9968be7..9ae0903bc225 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1621,6 +1621,12 @@ static int netfront_resume(struct xenbus_device *dev)
netif_tx_unlock_bh(info->netdev);
xennet_disconnect_backend(info);
+
+ rtnl_lock();
+ if (info->queues)
+ xennet_destroy_queues(info);
+ rtnl_unlock();
+
return 0;
}
