In the Linux kernel, the following vulnerability has been resolved: net: bonding: fix NULL...

In the Linux kernel, the following vulnerability has been resolved:

net: bonding: fix NULL pointer dereference in bond_do_ioctl()

In bond_do_ioctl(), slave_dev is obtained via __dev_get_by_name() which can return NULL if the requested interface name does not exist. However, the subsequent slave_dbg() call is placed before the NULL check:

slave_dev = __dev_get_by_name(net, ifr->ifr_slave);
slave_dbg(bond_dev, slave_dev, "slave_dev=%p:\n", slave_dev); //here
if (!slave_dev)
    return -ENODEV;

The slave_dbg() macro expands to netdev_dbg(bond_dev, "(slave %s): " fmt, (slave_dev)->name, ...) which unconditionally dereferences slave_dev->name before the NULL check is performed. This results in a NULL pointer dereference kernel oops when a user calls bonding ioctl (e.g. SIOCBONDENSLAVE, SIOCBONDRELEASE, etc.) with a non-existent slave interface name.

This is reachable from userspace via the bonding ioctl interface with CAP_NET_ADMIN capability, making it a potential local denial-of-service vector.

Fix by moving the slave_dbg() call after the NULL check.