[PATCH 6.12 147/265] wifi: mac80211: fix NULL pointer dereference in mesh_rx_csa_frame()

Greg Kroah-Hartman
2026-03-12T20:21:13Z

From: Vahagn Vardanian <vahagn@redrays.io>

commit 017c1792525064a723971f0216e6ef86a8c7af11 upstream.

In mesh_rx_csa_frame(), elems->mesh_chansw_params_ie is dereferenced
at lines 1638 and 1642 without a prior NULL check:

ifmsh->chsw_ttl = elems->mesh_chansw_params_ie->mesh_ttl;
...
pre_value = le16_to_cpu(elems->mesh_chansw_params_ie->mesh_pre_value);

The mesh_matches_local() check above only validates the Mesh ID,
Mesh Configuration, and Supported Rates IEs. It does not verify the
presence of the Mesh Channel Switch Parameters IE (element ID 118).
When a received CSA action frame omits that IE, ieee802_11_parse_elems()
leaves elems->mesh_chansw_params_ie as NULL, and the unconditional
dereference causes a kernel NULL pointer dereference.

A remote mesh peer with an established peer link (PLINK_ESTAB) can
trigger this by sending a crafted SPECTRUM_MGMT/CHL_SWITCH action frame
that includes a matching Mesh ID and Mesh Configuration IE but omits the
Mesh Channel Switch Parameters IE. No authentication beyond the default
open mesh peering is required.

Crash confirmed on kernel 6.17.0-5-generic via mac80211_hwsim:

BUG: kernel NULL pointer dereference, address: 0000000000000000
Oops: Oops: 0000 [#1] SMP NOPTI
RIP: 0010:ieee80211_mesh_rx_queued_mgmt+0x143/0x2a0 [mac80211]
CR2: 0000000000000000

Fix by adding a NULL check for mesh_chansw_params_ie after
mesh_matches_local() returns, consistent with how other optional IEs
are guarded throughout the mesh code.

The bug has been present since v3.13 (released 2014-01-19).

Fixes: 8f2535b92d68 ("mac80211: process the CSA frame for mesh accordingly")
Cc: stable@vger.kernel.org
Signed-off-by: Vahagn Vardanian <vahagn@redrays.io>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mac80211/mesh.c | 3 +++
1 file changed, 3 insertions(+)

--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -1631,6 +1631,9 @@ static void mesh_rx_csa_frame(struct iee
if (!mesh_matches_local(sdata, elems))
goto free;

+ if (!elems->mesh_chansw_params_ie)
+ goto free;
+
ifmsh->chsw_ttl = elems->mesh_chansw_params_ie->mesh_ttl;
if (!--ifmsh->chsw_ttl)
fwd_csa = false;