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authorLaurent Vivier <lvivier@redhat.com>2020-07-07 20:45:14 +0200
committerJason Wang <jasowang@redhat.com>2020-07-15 21:00:13 +0800
commit894022e616016fe81745753f14adfbd680a1c7ee (patch)
treefe44283139cd96b578d41ac420dfb06ec7efa7f6 /include/sysemu
parent2b28a7ef90d79ed757f6b1cc512840389dc25748 (diff)
net: check if the file descriptor is valid before using it
qemu_set_nonblock() checks that the file descriptor can be used and, if not, crashes QEMU. An assert() is used for that. The use of assert() is used to detect programming error and the coredump will allow to debug the problem. But in the case of the tap device, this assert() can be triggered by a misconfiguration by the user. At startup, it's not a real problem, but it can also happen during the hot-plug of a new device, and here it's a problem because we can crash a perfectly healthy system. For instance: # ip link add link virbr0 name macvtap0 type macvtap mode bridge # ip link set macvtap0 up # TAP=/dev/tap$(ip -o link show macvtap0 | cut -d: -f1) # qemu-system-x86_64 -machine q35 -device pcie-root-port,id=pcie-root-port-0 -monitor stdio 9<> $TAP (qemu) netdev_add type=tap,id=hostnet0,vhost=on,fd=9 (qemu) device_add driver=virtio-net-pci,netdev=hostnet0,id=net0,bus=pcie-root-port-0 (qemu) device_del net0 (qemu) netdev_del hostnet0 (qemu) netdev_add type=tap,id=hostnet1,vhost=on,fd=9 qemu-system-x86_64: .../util/oslib-posix.c:247: qemu_set_nonblock: Assertion `f != -1' failed. Aborted (core dumped) To avoid that, add a function, qemu_try_set_nonblock(), that allows to report the problem without crashing. In the same way, we also update the function for vhostfd in net_init_tap_one() and for fd in net_init_socket() (both descriptors are provided by the user and can be wrong). Signed-off-by: Laurent Vivier <lvivier@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com>
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