In the Linux kernel, the following vulnerability has been resolved:
ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce()
ethtool_set_coalesce() now uses both the .get_coalesce() and .set_coalesce() callbacks. But the check for their availability is buggy, so changing the coalesce settings on a device where the driver provides only _one_ of the callbacks results in a NULL pointer dereference instead of an -EOPNOTSUPP.
Fix the condition so that the availability of both callbacks is ensured. This also matches the netlink code.
Note that reproducing this requires some effort - it only affects the legacy ioctl path, and needs a specific combination of driver options:
- have .get_coalesce() and .coalesce_supported but no
- have .set_coalesce() but no .get_coalesce(). Here eg. ethtool doesn't