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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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fcb0bb6aab
The race may happen when a device (e.g. YOTA 4G LTE Modem) is
unplugged while the system is downloading a large file from the Net.
Hardware breakpoints and Kprobes with delays were used to confirm that
the race does actually happen.
The race is on skb_queue ('next' pointer) between usbnet_stop()
and rx_complete(), which, in turn, calls usbnet_bh().
Here is a part of the call stack with the code where the changes to the
queue happen. The line numbers are for the kernel 4.1.0:
*0 __skb_unlink (skbuff.h:1517)
prev->next = next;
*1 defer_bh (usbnet.c:430)
spin_lock_irqsave(&list->lock, flags);
old_state = entry->state;
entry->state = state;
__skb_unlink(skb, list);
spin_unlock(&list->lock);
spin_lock(&dev->done.lock);
__skb_queue_tail(&dev->done, skb);
if (dev->done.qlen == 1)
tasklet_schedule(&dev->bh);
spin_unlock_irqrestore(&dev->done.lock, flags);
*2 rx_complete (usbnet.c:640)
state = defer_bh(dev, skb, &dev->rxq, state);
At the same time, the following code repeatedly checks if the queue is
empty and reads these values concurrently with the above changes:
*0 usbnet_terminate_urbs (usbnet.c:765)
/* maybe wait for deletions to finish. */
while (!skb_queue_empty(&dev->rxq)
&& !skb_queue_empty(&dev->txq)
&& !skb_queue_empty(&dev->done)) {
schedule_timeout(msecs_to_jiffies(UNLINK_TIMEOUT_MS));
set_current_state(TASK_UNINTERRUPTIBLE);
netif_dbg(dev, ifdown, dev->net,
"waited for %d urb completions\n", temp);
}
*1 usbnet_stop (usbnet.c:806)
if (!(info->flags & FLAG_AVOID_UNLINK_URBS))
usbnet_terminate_urbs(dev);
As a result, it is possible, for example, that the skb is removed from
dev->rxq by __skb_unlink() before the check
"!skb_queue_empty(&dev->rxq)" in usbnet_terminate_urbs() is made. It is
also possible in this case that the skb is added to dev->done queue
after "!skb_queue_empty(&dev->done)" is checked. So
usbnet_terminate_urbs() may stop waiting and return while dev->done
queue still has an item.
Locking in defer_bh() and usbnet_terminate_urbs() was revisited to avoid
this race.
Signed-off-by: Eugene Shatokhin <eugene.shatokhin@rosalab.ru>
Reviewed-by: Bjørn Mork <bjorn@mork.no>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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| .. | ||
| asix_common.c | ||
| asix_devices.c | ||
| asix.h | ||
| ax88172a.c | ||
| ax88179_178a.c | ||
| catc.c | ||
| cdc_eem.c | ||
| cdc_ether.c | ||
| cdc_mbim.c | ||
| cdc_ncm.c | ||
| cdc_subset.c | ||
| cdc-phonet.c | ||
| cx82310_eth.c | ||
| dm9601.c | ||
| gl620a.c | ||
| hso.c | ||
| huawei_cdc_ncm.c | ||
| int51x1.c | ||
| ipheth.c | ||
| kalmia.c | ||
| kaweth.c | ||
| Kconfig | ||
| lan78xx.c | ||
| lan78xx.h | ||
| lg-vl600.c | ||
| Makefile | ||
| mcs7830.c | ||
| net1080.c | ||
| pegasus.c | ||
| pegasus.h | ||
| plusb.c | ||
| qmi_wwan.c | ||
| r8152.c | ||
| rndis_host.c | ||
| rtl8150.c | ||
| sierra_net.c | ||
| smsc75xx.c | ||
| smsc75xx.h | ||
| smsc95xx.c | ||
| smsc95xx.h | ||
| sr9700.c | ||
| sr9700.h | ||
| sr9800.c | ||
| sr9800.h | ||
| usbnet.c | ||
| zaurus.c | ||