Johannes pointed out that I have no clear link demonstrating that cfg80211_cqm_config_free is being called from cfg80211_cqm_rssi_notify.
Fair enough. So I compiled with
> void cfg80211_cqm_config_free(struct wireless_dev *wdev)
> {
> + pr_err("someone freeing the cqm_config");
> + dump_stack();
> kfree(wdev->cqm_config);
> wdev->cqm_config = NULL;
> }
And get the attached output.
Now I am out of ideas. This to me clearly looks like some kind of race. Freeing the cqm as part of netlink_sendmsg?
Maybe cfg80211_cqm_rssi_notify could just exit() when there currently is no station connected and thus avoid the null-ptr deref?
brcmfmac: brcmf_fil_cmd_data_set ifidx=0, cmd=52, len=12
brcmutil: data
00000000: 03 00 00 00 34 2c c4 3a 74 1f 37 da ....4,.:t.7.
brcmfmac: brcmf_rx_event Enter: mmc1:0001:1: rxp=ffffff8040227240
brcmfmac: brcmf_rx_event Enter: mmc1:0001:1: rxp=ffffff8040226340
brcmfmac: brcmf_fweh_event_worker event LINK (16) ifidx 0 bsscfg 0 addr xx:xx:xx:xx:74:1f
brcmfmac: brcmf_fweh_event_worker version 2 flags 0 status 0 reason 2
brcmutil: event payload, len=0
brcmfmac: brcmf_is_linkdown Processing link down
brcmfmac: brcmf_notify_connect_status Linkdown
brcmfmac: brcmf_fweh_event_worker event RSSI (56) ifidx 0 bsscfg 0 addr xx:xx:xx:xx:00:50
brcmfmac: brcmf_fweh_event_worker version 2 flags 0 status 0 reason 0
brcmutil: event payload, len=12
00000000: 00 00 00 00 00 00 00 00 00 00 00 00 ............
brcmfmac: brcmf_notify_rssi LOW rssi=0
brcmfmac: brcmf_cfg80211_del_key key index (0)
brcmfmac: brcmf_cfg80211_del_key Ignore clearing of (never configured) key
brcmfmac: brcmf_cfg80211_del_key key index (1)
brcmfmac: brcmf_cfg80211_del_key Ignore clearing of (never configured) key
brcmfmac: brcmf_cfg80211_del_key key index (2)
brcmfmac: brcmf_cfg80211_del_key Ignore clearing of (never configured) key
brcmfmac: brcmf_cfg80211_del_key key index (3)
brcmfmac: brcmf_cfg80211_del_key Ignore clearing of (never configured) key
brcmfmac: brcmf_cfg80211_del_key key index (4)
brcmfmac: brcmf_cfg80211_del_key Ignore clearing of (never configured) key
brcmfmac: brcmf_cfg80211_del_key key index (5)
brcmfmac: brcmf_cfg80211_del_key Ignore clearing of (never configured) key
brcmfmac: brcmf_fil_iovar_data_get ifidx=0, name=country, len=12, err=0
brcmutil: data
00000000: 44 45 00 00 00 00 00 00 44 45 00 41 DE......DE.A
cfg80211: someone freeing the cqm_config
CPU: 0 PID: 335 Comm: wpa_supplicant Tainted: G C 6.5.0-rc5-v8-gd9595c9a4f6d-dirty #7
Hardware name: Raspberry Pi Compute Module 4 Rev 1.0 (DT)
Call trace:
dump_backtrace (/home/r/linux/arch/arm64/kernel/stacktrace.c:235)
show_stack (/home/r/linux/arch/arm64/kernel/stacktrace.c:242)
dump_stack_lvl (/home/r/linux/lib/dump_stack.c:107)
dump_stack (/home/r/linux/lib/dump_stack.c:114)
cfg80211_cqm_config_free (/home/r/linux/net/wireless/core.c:1188) cfg80211
nl80211_set_cqm (/home/r/linux/net/wireless/core.h:239 /home/r/linux/net/wireless/nl80211.c:12883 /home/r/linux/net/wireless/nl80211.c:12955) cfg80211
genl_family_rcv_msg_doit.isra.0 (/home/r/linux/net/netlink/genetlink.c:970)
genl_rcv_msg (/home/r/linux/net/netlink/genetlink.c:1050 /home/r/linux/net/netlink/genetlink.c:1067)
netlink_rcv_skb (/home/r/linux/net/netlink/af_netlink.c:2549)
genl_rcv (/home/r/linux/net/netlink/genetlink.c:1079)
netlink_unicast (/home/r/linux/net/netlink/af_netlink.c:1340 /home/r/linux/net/netlink/af_netlink.c:1365)
netlink_sendmsg (/home/r/linux/net/netlink/af_netlink.c:1914)
sock_sendmsg (/home/r/linux/net/socket.c:725 /home/r/linux/net/socket.c:748)
____sys_sendmsg (/home/r/linux/net/socket.c:2494)
___sys_sendmsg (/home/r/linux/net/socket.c:2548)
__sys_sendmsg (/home/r/linux/./include/linux/file.h:32 /home/r/linux/net/socket.c:2579)
__arm64_sys_sendmsg (/home/r/linux/net/socket.c:2584)
invoke_syscall (/home/r/linux/arch/arm64/kernel/syscall.c:38 /home/r/linux/arch/arm64/kernel/syscall.c:52)
el0_svc_common.constprop.0 (/home/r/linux/./include/linux/thread_info.h:127 /home/r/linux/arch/arm64/kernel/syscall.c:147)
do_el0_svc (/home/r/linux/arch/arm64/kernel/syscall.c:189)
el0_svc (/home/r/linux/arch/arm64/kernel/entry-common.c:133 /home/r/linux/arch/arm64/kernel/entry-common.c:144 /home/r/linux/arch/arm64/kernel/entry-common.c:648)
el0t_64_sync_handler (/home/r/linux/arch/arm64/kernel/entry-common.c:666)
el0t_64_sync (/home/r/linux/arch/arm64/kernel/entry.S:591)
brcmfmac: brcmf_fil_cmd_data Firmware error: BCME_NOTFOUND (-30)
brcmfmac: brcmf_fil_iovar_data_get ifidx=0, name=tdls_sta_info, len=296, err=-52
brcmutil: data
00000000: 34 2c c4 3a 74 1f 00 00 00 00 00 00 00 00 00 00 4,.:t...........
00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
brcmfmac: brcmf_fil_cmd_data Firmware error: BCME_BADADDR (-21)
brcmfmac: brcmf_fil_iovar_data_get ifidx=0, name=sta_info, len=296, err=-52
brcmutil: data
00000000: 34 2c c4 3a 74 1f 00 00 00 00 00 00 00 00 00 00 4,.:t...........
00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
ieee80211 phy0: brcmf_cfg80211_get_station: GET STA INFO failed, -52
==================================================================
BUG: KASAN: null-ptr-deref in cfg80211_cqm_rssi_notify (/home/r/linux/net/wireless/nl80211.c:19089) cfg80211
Read of size 4 at addr 0000000000000004 by task kworker/0:2/38
Aug 12 09:28:20 hlcm4 kernel:
CPU: 0 PID: 38 Comm: kworker/0:2 Tainted: G C 6.5.0-rc5-v8-gd9595c9a4f6d-dirty #7
Hardware name: Raspberry Pi Compute Module 4 Rev 1.0 (DT)
Workqueue: events brcmf_fweh_event_worker [brcmfmac]
Call trace:
dump_backtrace (/home/r/linux/arch/arm64/kernel/stacktrace.c:235)
show_stack (/home/r/linux/arch/arm64/kernel/stacktrace.c:242)
dump_stack_lvl (/home/r/linux/lib/dump_stack.c:107)
kasan_report (/home/r/linux/mm/kasan/report.c:590)
__asan_load4 (/home/r/linux/mm/kasan/generic.c:259)
cfg80211_cqm_rssi_notify (/home/r/linux/net/wireless/nl80211.c:19089) cfg80211
brcmf_notify_rssi (/home/r/linux/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:6651) brcmfmac
brcmf_fweh_call_event_handler (/home/r/linux/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c:109) brcmfmac
brcmf_fweh_event_worker (/home/r/linux/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c:268) brcmfmac
process_one_work (/home/r/linux/./arch/arm64/include/asm/jump_label.h:21 /home/r/linux/./include/linux/jump_label.h:207 /home/r/linux/./include/trace/events/workqueue.h:108 /home/r/linux/kernel/workqueue.c:2602)
worker_thread (/home/r/linux/./include/linux/list.h:292 /home/r/linux/kernel/workqueue.c:2749)
kthread (/home/r/linux/kernel/kthread.c:389)
ret_from_fork (/home/r/linux/arch/arm64/kernel/entry.S:854)
==================================================================
Disabling lock debugging due to kernel taint
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004
Mem abort info:
ESR = 0x0000000096000005
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x05: level 1 translation fault
Data abort info:
ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 39-bit VAs, pgdp=000000004c5c2000
brcmfmac: brcmf_fil_iovar_data_set ifidx=0, name=rssi_event, len=16
[0000000000000004] pgd=0000000000000000
brcmutil: data
, p4d=0000000000000000, pud=0000000000000000
00000000: 00 00 00 00 03 00 00 7f 00 00 00 00 00 00 00 00 ................
Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
Modules linked in: brcmfmac_wcc brcmfmac cfg80211 rpivid_hevc(C) bcm2835_isp(C) rtc_pcf85063 bcm2835_mmal_vchiq(C) regmap_i2c xt_tcpudp nft_compat videobuf2_dma_contig v3d videobuf2_memops nf_tables v4l2_mem2mem videobuf2_v4l2 videodev nfnetlink drm_shmem_helper gpu_sched i2c_mux_pinctrl gpio_keys i2c_mux hid_microsoft raspberrypi_hwmon videobuf2_common joydev ff_memless rfkill brcmutil i2c_brcmstb i2c_bcm2835 vc_sm_cma(C) mc uio_pdrv_genirq nvmem_rmem uio drm fuse drm_panel_orientation_quirks backlight ip_tables x_tables ipv6
CPU: 0 PID: 38 Comm: kworker/0:2 Tainted: G B C 6.5.0-rc5-v8-gd9595c9a4f6d-dirty #7
Hardware name: Raspberry Pi Compute Module 4 Rev 1.0 (DT)
Workqueue: events brcmf_fweh_event_worker [brcmfmac]
pstate: 40000005 (nZcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : cfg80211_cqm_rssi_notify (/home/r/linux/net/wireless/nl80211.c:19089) cfg80211
lr : cfg80211_cqm_rssi_notify (/home/r/linux/net/wireless/nl80211.c:19089) cfg80211
sp : ffffffc0805c7a10
x29: ffffffc0805c7a10 x28: 0000000000000001 x27: ffffff804743a368
x26: ffffff80428883c0 x25: 1ffffff8100b8f4e x24: ffffff804c1496d0
x23: 0000000000000cc0 x22: 0000000000000000 x21: ffffff804743a008
x20: 0000000000000000 x19: ffffff804c0ac000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 746e696174206c65 x12: ffffffbde8d1dc29
x11: 1ffffffde8d1dc28 x10: ffffffbde8d1dc28 x9 : dfffffc000000000
x8 : 00000042172e23d8 x7 : ffffffef468ee147 x6 : 0000000000000001
x5 : ffffffef468ee140 x4 : ffffffbde8d1dc29 x3 : ffffffef440c0924
x2 : 0000000000000000 x1 : ffffff8040b6a0c0 x0 : 0000000000000001
Call trace:
cfg80211_cqm_rssi_notify (/home/r/linux/net/wireless/nl80211.c:19089) cfg80211
brcmf_notify_rssi (/home/r/linux/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:6651) brcmfmac
brcmf_fweh_call_event_handler (/home/r/linux/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c:109) brcmfmac
brcmf_fweh_event_worker (/home/r/linux/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c:268) brcmfmac
process_one_work (/home/r/linux/./arch/arm64/include/asm/jump_label.h:21 /home/r/linux/./include/linux/jump_label.h:207 /home/r/linux/./include/trace/events/workqueue.h:108 /home/r/linux/kernel/workqueue.c:2602)
worker_thread (/home/r/linux/./include/linux/list.h:292 /home/r/linux/kernel/workqueue.c:2749)
kthread (/home/r/linux/kernel/kthread.c:389)
ret_from_fork (/home/r/linux/arch/arm64/kernel/entry.S:854)
Code: 9401bd4d f941b2b4 91001280 9401bd44 (b9400694)
All code
========
0: 9401bd4d bl 0x6f534
4: f941b2b4 ldr x20, [x21, #864]
8: 91001280 add x0, x20, #0x4
c: 9401bd44 bl 0x6f51c
10:* b9400694 ldr w20, [x20, #4] <-- trapping instruction
Code starting with the faulting instruction
===========================================
0: b9400694 ldr w20, [x20, #4]
---[ end trace 0000000000000000 ]---
brcmfmac: brcmf_fil_iovar_data_get ifidx=0, name=qtxpower, len=4, err=0
brcmutil: data
00000000: 7f 00 00 00 ....
brcmfmac: brcmf_fil_iovar_data_set ifidx=0, name=mcast_list, len=22
