for n in $( seq 1 250 ) ; do
echo $n
( dd if=/dev/zero of=/dev/nbd0 bs=1 & )
done
qemu-nbd -d /dev/nbd0
after running that, on an unpatched system the dmesg will show a large number (~100 or more) of messages like:
[ 70.408246] block nbd0: Attempted send on closed socket
with a patched kernel, the dmesg will show a ratelimited number (~10) of those messages.
This has been verified on trusty 3.13, vivid 3.19, and wily 4.2
verification can be done with this script:
#!/bin/bash
modprobe nbd
qemu-nbd -d /dev/nbd0
truncate /tmp/testfile -s 20G
qemu-nbd -c /dev/nbd0 /tmp/testfile
for n in $( seq 1 250 ) ; do
echo $n
( dd if=/dev/zero of=/dev/nbd0 bs=1 & )
done
qemu-nbd -d /dev/nbd0
after running that, on an unpatched system the dmesg will show a large number (~100 or more) of messages like:
[ 70.408246] block nbd0: Attempted send on closed socket
with a patched kernel, the dmesg will show a ratelimited number (~10) of those messages.
This has been verified on trusty 3.13, vivid 3.19, and wily 4.2