published December 8, 2025
In the Linux kernel, the following vulnerability has been resolved:
wifi: brcmfmac: fix crash while sending Action Frames in standalone AP Mode
Currently, whenever there is a need to transmit an Action frame,
the brcmfmac driver always uses the P2P vif to send the "actframe" IOVAR to
firmware. The P2P interfaces were available when wpa_supplicant is managing
the wlan interface.
However, the P2P interfaces are not created/initialized when only hostapd
is managing the wlan interface. And if hostapd receives an ANQP Query REQ
Action frame even from an un-associated STA, the brcmfmac driver tries
to use an uninitialized P2P vif pointer for sending the IOVAR to firmware.
This NULL pointer dereferencing triggers a driver crash.
[ 1417.074538] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000000
[...]
[ 1417.075188] Hardware name: Raspberry Pi 4 Model B Rev 1.5 (DT)
[...]
[ 1417.075653] Call trace:
[ 1417.075662] brcmf_p2p_send_action_frame+0x23c/0xc58 [brcmfmac]
[ 1417.075738] brcmf_cfg80211_mgmt_tx+0x304/0x5c0 [brcmfmac]
[ 1417.075810] cfg80211_mlme_mgmt_tx+0x1b0/0x428 [cfg80211]
[ 1417.076067] nl80211_tx_mgmt+0x238/0x388 [cfg80211]
[ 1417.076281] genl_family_rcv_msg_doit+0xe0/0x158
[ 1417.076302] genl_rcv_msg+0x220/0x2a0
[ 1417.076317] netlink_rcv_skb+0x68/0x140
[ 1417.076330] genl_rcv+0x40/0x60
[ 1417.076343] netlink_unicast+0x330/0x3b8
[ 1417.076357] netlink_sendmsg+0x19c/0x3f8
[ 1417.076370] __sock_sendmsg+0x64/0xc0
[ 1417.076391] ____sys_sendmsg+0x268/0x2a0
[ 1417.076408] ___sys_sendmsg+0xb8/0x118
[ 1417.076427] __sys_sendmsg+0x90/0xf8
[ 1417.076445] __arm64_sys_sendmsg+0x2c/0x40
[ 1417.076465] invoke_syscall+0x50/0x120
[ 1417.076486] el0_svc_common.constprop.0+0x48/0xf0
[ 1417.076506] do_el0_svc+0x24/0x38
[ 1417.076525] el0_svc+0x30/0x100
[ 1417.076548] el0t_64_sync_handler+0x100/0x130
[ 1417.076569] el0t_64_sync+0x190/0x198
[ 1417.076589] Code: f9401e80 aa1603e2 f9403be1 5280e483 (f9400000)
Fix this, by always using the vif corresponding to the wdev on which the
Action frame Transmission request was initiated by the userspace. This way,
even if P2P vif is not available, the IOVAR is sent to firmware on AP vif
and the ANQP Query RESP Action frame is transmitted without crashing the
driver.
Move init_completion() for "send_af_done" from brcmf_p2p_create_p2pdev()
to brcmf_p2p_attach(). Because the former function would not get executed
when only hostapd is managing wlan interface, and it is not safe to do
reinit_completion() later in brcmf_p2p_tx_action_frame(), without any prior
init_completion().
And in the brcmf_p2p_tx_action_frame() function, the condition check for
P2P Presence response frame is not needed, since the wpa_supplicant is
properly sending the P2P Presense Response frame on the P2P-GO vif instead
of the P2P-Device vif.
[Cc stable]