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:

ieee80211leavemesh() -> kfree(sdata->u.mesh.ie); ... ieee80211joinmesh() -> copymeshsetup() -> oldie = ifmsh->ie; -> kfree(oldie);

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 wpasupplicant. And it seems that wpasupplicant or wpacli are going through a NETDEVDOWN/NETDEVUP cycle between a mesh leave and mesh join where the NETDEVUP resets the mesh.ie to NULL via a memcpy of defaultmeshsetup in cfg80211netdevnotifier_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.