CVE-2022-49290

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

mac80211: fix potential double free on mesh join

While commit 6a01afcf8468 ("mac80211: mesh: Free ie data when leaving mesh") fixed a memory leak on mesh leave / teardown it introduced a potential memory corruption caused by a double free when rejoining the mesh:

ieee80211_leave_mesh() -> kfree(sdata->u.mesh.ie); ... ieee80211_join_mesh() -> copy_mesh_setup() -> old_ie = ifmsh->ie; -> kfree(old_ie);

This double free / kernel panics can be reproduced by using wpa_supplicant with an encrypted mesh (if set up without encryption via "iw" then ifmsh->ie is always NULL, which avoids this issue). And then calling:

$ iw dev mesh0 mesh leave $ iw dev mesh0 mesh join my-mesh

Note that typically these commands are not used / working when using wpa_supplicant. And it seems that wpa_supplicant or wpa_cli are going through a NETDEV_DOWN/NETDEV_UP cycle between a mesh leave and mesh join where the NETDEV_UP resets the mesh.ie to NULL via a memcpy of default_mesh_setup in cfg80211_netdev_notifier_call, which then avoids the memory corruption, too.

The issue was first observed in an application which was not using wpa_supplicant but "Senf" instead, which implements its own calls to nl80211.

Fixing the issue by removing the kfree()'ing of the mesh IE in the mesh join function and leaving it solely up to the mesh leave to free the mesh IE.

This flaw is rated as Moderate impact for Red Hat Enterprise Linux because exploitation requires local access with privileges to configure wireless network interfaces, limiting the attack surface to systems with active wireless hardware. In enterprise server environments, wireless networking and IEEE 802.11 mesh configurations are rarely deployed by default. Furthermore, standard network management workflows normally cycle device states between mesh operations, which resets the associated interface structures and avoids triggering the double free condition.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.