CVE-2024-26596

/// Technical description

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

net: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events

After the blamed commit, we started doing this dereference for every

NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER event in the system.

static inline struct dsa_port *dsa_user_to_port(const struct net_device *dev)

{

struct dsa_user_priv *p = netdev_priv(dev);

return p->dp;

}

Which is obviously bogus, because not all net_devices have a netdev_priv()

of type struct dsa_user_priv. But struct dsa_user_priv is fairly small,

and p->dp means dereferencing 8 bytes starting with offset 16. Most

drivers allocate that much private memory anyway, making our access not

fault, and we discard the bogus data quickly afterwards, so this wasn't

caught.

But the dummy interface is somewhat special in that it calls

alloc_netdev() with a priv size of 0. So every netdev_priv() dereference

is invalid, and we get this when we emit a NETDEV_PRECHANGEUPPER ev

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References