mesh_matches_local() unconditionally dereferences ie->mesh_config to compare mesh configuration parameters. When called from mesh_rx_csa_frame(), the parsed action-frame elements may not contain a Mesh Configuration IE, leaving ie->mesh_config NULL and triggering a kernel NULL pointer dereference. The other two callers are already safe: - ieee80211_mesh_rx_bcn_presp() checks !elems->mesh_config before calling mesh_matches_local() - mesh_plink_get_event() is only reached through mesh_process_plink_frame(), which checks !elems->mesh_config, too mesh_rx_csa_frame() is the only caller that passes raw parsed elements to mesh_matches_local() without guarding mesh_config. An adjacent attacker can exploit this by sending a crafted CSA action frame that includes a valid Mesh ID IE but omits the Mesh Configuration IE, crashing the kernel. The captured crash log: Oops: general protection fault, probably for non-canonical address ... KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] Workqueue: events_unbound cfg80211_wiphy_work [...] Call Trace: ? __pfx_mesh_matches_local (net/mac80211/mesh.c:65) ieee80211_mesh_rx_queued_mgmt (net/mac80211/mesh.c:1686) [...] ieee80211_iface_work (net/mac80211/iface.c:1754 net/mac80211/iface.c:1802) [...] cfg80211_wiphy_work (net/wireless/core.c:426) process_one_work (net/kernel/workqueue.c:3280) ? assign_work (net/kernel/workqueue.c:1219) worker_thread (net/kernel/workqueue.c:3352) ? __pfx_worker_thread (net/kernel/workqueue.c:3385) kthread (net/kernel/kthread.c:436) [...] ret_from_fork_asm (net/arch/x86/entry/entry_64.S:255) This patch adds a NULL check for ie->mesh_config at the top of mesh_matches_local() to return false early when the Mesh Configuration IE is absent. Fixes: 2e3c8736820b ("mac80211: support functions for mesh") Reported-by: Weiming Shi Signed-off-by: Xiang Mei --- net/mac80211/mesh.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c index 28624e57aa499..8fdbdf9ba2a9e 100644 --- a/net/mac80211/mesh.c +++ b/net/mac80211/mesh.c @@ -79,6 +79,9 @@ bool mesh_matches_local(struct ieee80211_sub_if_data *sdata, * - MDA enabled * - Power management control on fc */ + if (!ie->mesh_config) + return false; + if (!(ifmsh->mesh_id_len == ie->mesh_id_len && memcmp(ifmsh->mesh_id, ie->mesh_id, ie->mesh_id_len) == 0 && (ifmsh->mesh_pp_id == ie->mesh_config->meshconf_psel) && -- 2.43.0