wifi: mac80211: account proxy paths against the mesh path limit

Overview

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

wifi: mac80211: account proxy paths against the mesh path limit

Proxy-path churn can drive the interface path counter negative and let later mesh path additions exceed MESH_MAX_MPATHS.

mesh_path_free_rcu() decrements the interface mpaths counter for entries from both the mesh and proxy path tables, but mpp_path_add() never reserves a slot in that counter. Removing or expiring a proxy path therefore returns a slot that was never charged.

mesh_path_add() uses the same counter to enforce MESH_MAX_MPATHS, so once it falls below the number of installed paths the limit no longer holds.

Reserve the shared quota before allocating a proxy path and release it on every unsuccessful addition. Mesh and proxy paths now share one 1024-entry budget, so mpp_path_add() can return -ENOSPC at that limit.

Affected

• Linux >= ece1a2e7e86078c8379937b546e32cb7f25fcb6c < c66ab4b94bb04c162485759196555e08c0965320
• Linux >= ece1a2e7e86078c8379937b546e32cb7f25fcb6c < df072db65fdaa34ad15e1d66fc06a53e3e97f778
• Linux >= ece1a2e7e86078c8379937b546e32cb7f25fcb6c < 3b75831ceee76d32bb8e7ddd241904f92f9b5407
• Linux >= ece1a2e7e86078c8379937b546e32cb7f25fcb6c < 5a32409ed34a1868830899a5d2437f0b3bf3532c
• Linux >= ece1a2e7e86078c8379937b546e32cb7f25fcb6c < a5f35d4b112af1415ff06bd501c8cc26cc08aa8b
• Linux 3.2

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.