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. Fixes: e2a7420df2e0 ("bonding/main: convert to using slave printk macros") Cc: stable@vger.kernel.org # v5.2+ Signed-off-by: ZhaoJinming --- drivers/net/bonding/bond_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 82e779f7916b..8e75453ce0ef 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -4621,11 +4621,11 @@ static int bond_do_ioctl(struct net_device *bond_dev, struct ifreq *ifr, int cmd slave_dev = __dev_get_by_name(net, ifr->ifr_slave); - slave_dbg(bond_dev, slave_dev, "slave_dev=%p:\n", slave_dev); - if (!slave_dev) return -ENODEV; + slave_dbg(bond_dev, slave_dev, "slave_dev=%p:\n", slave_dev); + switch (cmd) { case SIOCBONDENSLAVE: res = bond_enslave(bond_dev, slave_dev, NULL); -- 2.20.1