Hello! I have cross-compiled a kernel (5.6.2) for ARM with the module br_netfilter included. When I load the module using modprobe br_netfilter on my ARM machine I get a segfault resulting in text on the screen and in dmesg. Output of gdb shows this: (gdb) file br_netfilter.ko (gdb) list *brnf_init_net+0x90 0x388 is in brnf_init_net (net/bridge/br_netfilter_hooks.c:1110). Line 1110 of net/bridge/br_netfilter_hooks.c is: br_netfilter_sysctl_default(brnet); Kernel information Kernel version (from /proc/version): Host machine: Linux version 5.4.0-rc5-custom (temrix@msi-pc) (gcc version 8.3.0 (Debian 8.3.0-6)) #2 SMP Tue Oct 29 22:45:09 CET 2019 ARM machine: Linux version 5.6.2 (temrix@msi-pc) (gcc version 9.2.1 20191025 (GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10))) #1 SMP Fri Apr 3 21:05:22 CEST 2020 Cross-compile toolchain: gcc-arm-9.2-2019.12-x86_64-arm-none-linux-gnueabihf Kernel .config file: see attachments Most recent kernel version I tried which did not have the bug: 5.4.0-rc5_armhf Output of dmesg: resolved (see Documentation/admin-guide/bug-hunting.rst) [ 538.272076] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this. [ 538.289383] 8<--- cut here --- [ 538.292447] Unable to handle kernel NULL pointer dereference at virtual address 00000008 [ 538.300638] pgd = c483f76c [ 538.303357] [00000008] *pgd=00000000 [ 538.307021] Internal error: Oops: 805 [#1] SMP ARM [ 538.311804] Modules linked in: br_netfilter(+) bridge stp llc iptable_filter overlay uas usb_storage ip_tables x_tables [ 538.322595] CPU: 0 PID: 6089 Comm: modprobe Not tainted 5.6.2 #1 [ 538.328590] Hardware name: Allwinner A83t board [ 538.333138] PC is at brnf_init_net+0x90/0xe4 [br_netfilter] [ 538.338715] LR is at ops_init+0x38/0xf0 [ 538.342544] pc : [<bf07e388>] lr : [<c06264f8>] psr: 60010013 [ 538.348801] sp : ea105d58 ip : ec056500 fp : 00000000 [ 538.354018] r10: bf082140 r9 : ec056ac0 r8 : c0b6b100 [ 538.359236] r7 : c0b6b100 r6 : 00000000 r5 : bf082000 r4 : 00000000 [ 538.365753] r3 : 00000001 r2 : bf082000 r1 : bf081114 r0 : c0b6b100 [ 538.372272] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none [ 538.379399] Control: 10c5387d Table: 6a26806a DAC: 00000051 [ 538.385139] Process modprobe (pid: 6089, stack limit = 0x9f8e5438) [ 538.391311] Stack: (0xea105d58 to 0xea106000) [ 538.395664] 5d40: ec0564c0 bf08210c [ 538.403830] 5d60: c0b6b100 0000000a ee984000 c06264f8 bf08210c c0b6b100 0000000a ea105d94 [ 538.411998] 5d80: c0b6b058 ec056ac0 bf082140 c06268a0 00000000 ea105d94 ea105d94 c0b04e48 [ 538.420165] 5da0: c0b6b040 bf08210c ffffe000 00000000 bf082188 c06269c4 c0b75e40 bf085000 [ 538.428333] 5dc0: ffffe000 bf08500c c0b75e40 c01026d0 ee815c00 ec08db00 edc042c0 ef42b3d4 [ 538.436500] 5de0: ee803e00 ec08db80 ef42b3d4 8040003e ec08db80 c0210a10 bf082188 c0b04e48 [ 538.444667] 5e00: 00000001 ef42b3d4 ee803e00 ec08db00 c01a1354 bf082188 bf082140 c0b04e48 [ 538.452835] 5e20: 00000002 bf082140 ec056880 00000002 00000002 c019f1e4 ec056a80 00000002 [ 538.461002] 5e40: ea105f40 ec056a80 00000002 c01a135c bf08214c 00007fff bf082140 c019e400 [ 538.469169] 5e60: bf082318 00000000 c0803038 c090733c bf08214c bf087150 bf082254 c0907294 [ 538.477337] 5e80: c09072ec ea105f38 004c7498 c023ec68 00000000 00000000 00000000 ffffe000 [ 538.485503] 5ea0: 00000000 00000000 00000000 00000000 00000000 00000000 6e72656b 00006c65 [ 538.493670] 5ec0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 538.501836] 5ee0: 00000000 00000000 00000000 00000000 00000000 c0b04e48 7fffffff 00000000 [ 538.510004] 5f00: 00000006 004b17e0 0000017b c0101204 ea104000 0000017b 004c7498 c01a199c [ 538.518173] 5f20: 7fffffff 00000000 00000003 000000c0 004c7498 f0bf4000 00004cbc 00000000 [ 538.526341] 5f40: f0bf65bf f0bf6780 f0bf4000 00004cbc f0bf858c f0bf83c0 f0bf7584 00005000 [ 538.534507] 5f60: 00005220 000020dc 00005403 00000000 00000000 00000000 000020cc 0000002b [ 538.542674] 5f80: 0000002c 00000021 00000000 00000017 0000001d c0b04e48 004b310c 00000000 [ 538.550842] 5fa0: b0b55500 c0101000 004b310c 00000000 00000006 004b17e0 00000000 004b3318 [ 538.559010] 5fc0: 004b310c 00000000 b0b55500 0000017b 004c74e8 00000000 00000000 004c7498 [ 538.567176] 5fe0: be916398 be916388 004a9e41 b6ceed92 40010030 00000006 00000000 00000000 [ 538.575373] [<bf07e388>] (brnf_init_net [br_netfilter]) from [<c06264f8>] (ops_init+0x38/0xf0) [ 538.583982] [<c06264f8>] (ops_init) from [<c06268a0>] (register_pernet_operations+0xf4/0x1f4) [ 538.592499] [<c06268a0>] (register_pernet_operations) from [<c06269c4>] (register_pernet_subsys+0x24/0x38) [ 538.602145] [<c06269c4>] (register_pernet_subsys) from [<bf08500c>] (br_netfilter_init+0xc/0x1000 [br_netfilter]) [ 538.612403] [<bf08500c>] (br_netfilter_init [br_netfilter]) from [<c01026d0>] (do_one_initcall+0x58/0x1c4) [ 538.622051] [<c01026d0>] (do_one_initcall) from [<c019f1e4>] (do_init_module+0x5c/0x244) [ 538.630138] [<c019f1e4>] (do_init_module) from [<c01a135c>] (load_module+0x1f0c/0x22ec) [ 538.638134] [<c01a135c>] (load_module) from [<c01a199c>] (sys_finit_module+0xd0/0xe8) [ 538.645956] [<c01a199c>] (sys_finit_module) from [<c0101000>] (ret_fast_syscall+0x0/0x54) [ 538.654120] Exception stack(0xea105fa8 to 0xea105ff0) [ 538.659166] 5fa0: 004b310c 00000000 00000006 004b17e0 00000000 004b3318 [ 538.667334] 5fc0: 004b310c 00000000 b0b55500 0000017b 004c74e8 00000000 00000000 004c7498 [ 538.675499] 5fe0: be916398 be916388 004a9e41 b6ceed92 [ 538.680547] Code: e58520b8 e3011114 e1a02005 e34b1f08 (e5843008) [ 538.686793] ---[ end trace c644a87d777f3f88 ]--- A small shell script or example program which triggers the problem modprobe br_netfilter Environment output of the ver_linux script: Host machine: If some fields are empty or look unusual you may have an old version. Compare to the current minimal requirements in Documentation/Changes. Linux msi-pc 5.4.0-rc5-custom #2 SMP Tue Oct 29 22:45:09 CET 2019 x86_64 GNU/Linux GNU Make 4.2.1 Binutils 2.31.1 Util-linux 2.33.1 Mount 2.33.1 Bison 3.3.2 Flex 2.6.4 Linux C Library 2.28 Dynamic linker (ldd) 2.28 Procps 3.3.15 Kbd 2.0.4 Console-tools 2.0.4 Sh-utils 8.30 Udev 241 Modules Loaded acpi_pad aesni_intel ahci autofs4 binfmt_misc button coretemp crc16 crc32c_generic crc32c_intel crc32_pclmul crct10dif_pclmul cryptd crypto_simd drm drm_kms_helper efi_pstore efivarfs efivars evdev ext4 fan fat fuse ghash_clmulni_intel glue_helper gspca_main gspca_sonixj hid hid_generic i2c_i801 intel_cstate intel_powerclamp intel_rapl_common intel_rapl_msr intel_rapl_perf intel_uncore ipmi_devintf ipmi_msghandler ip_tables irqbypass iTCO_vendor_support iTCO_wdt jbd2 kvm kvm_intel ledtrig_audio libahci libata libphy lp mbcache mc mei mei_me mxm_wmi nls_ascii nls_cp437 nvidia nvidia_drm nvidia_modeset nvme nvme_core overlay parport parport_pc pcspkr ppdev r8169 realtek scsi_mod sd_mod sg snd snd_hda_codec snd_hda_codec_generic snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_core snd_hda_intel snd_hwdep snd_intel_nhlt snd_pcm snd_rawmidi snd_seq_device snd_timer snd_usb_audio snd_usbmidi_lib soundcore thermal uas usbcore usbhid usb_storage vfat video videobuf2_common videobuf2_memops videobuf2_v4l2 videobuf2_vmalloc videodev wmi x86_pkg_temp_thermal xhci_hcd xhci_pci x_tables ARM machine: If some fields are empty or look unusual you may have an old version. Compare to the current minimal requirements in Documentation/Changes. Linux cubietruck-plus 5.6.2 #1 SMP Fri Apr 3 21:05:22 CEST 2020 armv7l GNU/Linux GNU Make 4.2.1 Binutils 2.31.1 Util-linux 2.33.1 Mount 2.33.1 Linux C Library 2.28 Dynamic linker (ldd) 2.28 Procps 3.3.15 Sh-utils 8.30 Udev 241 Modules Loaded iptable_filter ip_tables overlay uas usb_storage x_tables Processor information (from /proc/cpuinfo): ARM machine: model name : ARMv7 Processor rev 5 (v7l) BogoMIPS : 57.14 Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm CPU implementer : 0x41 CPU architecture: 7 CPU variant : 0x0 CPU part : 0xc07 CPU revision : 5 Hardware : Allwinner A83t board Revision : 0000 Serial : 32c00001b3cbac18 Module information (from /proc/modules): ARM machine: br_netfilter 36864 1 - Loading 0x00000000 bridge 143360 1 br_netfilter, Live 0x00000000 stp 16384 1 bridge, Live 0x00000000 llc 16384 2 bridge,stp, Live 0x00000000 iptable_filter 16384 1 - Live 0x00000000 overlay 90112 0 - Live 0x00000000 uas 20480 0 - Live 0x00000000 usb_storage 53248 2 uas, Live 0x00000000 ip_tables 24576 1 iptable_filter, Live 0x00000000 x_tables 24576 2 iptable_filter,ip_tables, Live 0x00000000 Loaded driver and hardware information (/proc/iomem) ARM machine: 00000000-00000000 : 1000000.clock 00000000-00000000 : sunxi-mc-smp 00000000-00000000 : 1c02000.dma-controller 00000000-00000000 : 1c0f000.mmc 00000000-00000000 : 1c10000.mmc 00000000-00000000 : 1c11000.mmc 00000000-00000000 : 1c14000.eeprom 00000000-00000000 : usb@1c19000 00000000-00000000 : musb-hdrc.1.auto 00000000-00000000 : 1c19400.phy 00000000-00000000 : 1c1a000.usb 00000000-00000000 : 1c19400.phy 00000000-00000000 : 1c1b000.usb 00000000-00000000 : 1c19400.phy 00000000-00000000 : 1c20000.clock 00000000-00000000 : 1c20800.pinctrl 00000000-00000000 : 1c20ca0.watchdog 00000000-00000000 : serial 00000000-00000000 : serial 00000000-00000000 : 1c30000.ethernet 00000000-00000000 : interrupt-controller@1f00c00 00000000-00000000 : clock@1f01400 00000000-00000000 : sunxi-mc-smp 00000000-00000000 : 1f02c00.pinctrl 00000000-00000000 : 1f03400.rsb 00000000-00000000 : 1f04000.thermal-sensor 00000000-00000000 : System RAM 00000000-00000000 : Kernel code 00000000-00000000 : Kernel data
