Messages in this thread | | | From | Josh Elsasser <> | Subject | [PATCH 0/1] net: avoid a kernel panic during sk_busy_loop | Date | Mon, 12 Mar 2018 22:31:59 -0700 |
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V2: just check napi->dev->netdev_ops instead of getting clever with the netdev registration state.
Original cover letter:
Hi Dave,
I stumbled across a reproducible kernel panic while playing around with busy_poll on a Linux 4.9.86 kernel. There's an unfortunate interaction between init_dummy_netdev, which doesn't bother to fill in netdev_ops, and sk_busy_loop, which assumed netdev_ops is a valid pointer.
To reproduce on the device under test (DUT), I did:
$ ip addr show dev wlan0 8: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq [...] inet 172.16.122.6/23 brd 172.16.123.255 scope global wlan0 $ sysctl -w net.core.busy_read=50 $ nc -l 172.16.122.6 5001
Then transmitted some data to this socket from a second host:
$ echo "foo" | nc 172.16.122.6 5001
The DUT immediately hits a kernel panic.
I've attached a patch that applies cleanly to the 4.9.87 stable release. This fix isn't necessary for net/net-next (ndo_busy_poll was removed in linux-4.11), but a further backport of this commit is likely required for any stable releases older than linux-4.5.
I hope this is the right way to raise something like this. I couldn't find a clear answer from the -stable and netdev on how to handle bugs in features that no longer exist in mainline.
Thanks, Josh
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