next-20230110: arm64: defconfig+kselftest config boot failed - Unable to handle kernel paging request at virtual address fffffffffffffff8

Tue Jan 10 16:41:08 UTC 2023

On Tue, Jan 10, 2023, at 17:14, Naresh Kamboju wrote:
> [ please ignore this email if this regression already reported ]
>
> Today's Linux next tag next-20230110 boot passes with defconfig but
> boot fails with
> defconfig + kselftest merge config on arm64 devices and qemu-arm64.
>
> Reported-by: Linux Kernel Functional Testing <lkft at linaro.org>
>
> We are bisecting this problem and get back to you shortly.
>
> GOOD: next-20230109  (defconfig + kselftests configs)
> BAD: next-20230110 (defconfig + kselftests configs)
>
> kernel crash log [1]:
>
> [   15.302140] Unable to handle kernel paging request at virtual
> address fffffffffffffff8
> [   15.309906] Mem abort info:
> [   15.312659]   ESR = 0x0000000096000004
> [   15.316365]   EC = 0x25: DABT (current EL), IL = 32 bits
> [   15.321626]   SET = 0, FnV = 0
> [   15.324644]   EA = 0, S1PTW = 0
> [   15.327744]   FSC = 0x04: level 0 translation fault
> [   15.332619] Data abort info:
> [   15.335422]   ISV = 0, ISS = 0x00000004
> [   15.339226]   CM = 0, WnR = 0
> [   15.342154] swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000001496c000
> [   15.348795] [fffffffffffffff8] pgd=0000000000000000, p4d=0000000000000000
> [   15.355524] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
> [   15.361729] Modules linked in: meson_gxl dwmac_generic
> snd_soc_meson_gx_sound_card snd_soc_meson_card_utils lima gpu_sched
> drm_shmem_helper meson_drm drm_dma_helper crct10dif_ce meson_ir
> rc_core meson_dw_hdmi dw_hdmi meson_canvas dwmac_meson8b
> stmmac_platform meson_rng stmmac rng_core cec meson_gxbb_wdt
> drm_display_helper snd_soc_meson_aiu snd_soc_meson_codec_glue pcs_xpcs
> snd_soc_meson_t9015 amlogic_gxl_crypto crypto_engine display_connector
> snd_soc_simple_amplifier drm_kms_helper drm nvmem_meson_efuse
> [   15.405976] CPU: 1 PID: 9 Comm: kworker/u8:0 Not tainted
> 6.2.0-rc3-next-20230110 #1
> [   15.413563] Hardware name: Libre Computer AML-S905X-CC (DT)
> [   15.419086] Workqueue: events_unbound deferred_probe_work_func
> [   15.424863] pstate: 00000005 (nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   15.431762] pc : of_drm_find_bridge+0x38/0x70 [drm]
> [   15.436594] lr : of_drm_find_bridge+0x20/0x70 [drm]

The line is 

drivers/gpu/drm/drm_bridge.c:1310:      if (bridge->of_node == np) {

The list_head here is a NULL pointer, so ->of_node points
to address negative 8, i.e. fffffffffffffff8

This is linked list corruption, which typically happens as
part of a use-after-free, and could be the result of a
failed registration causing an object to be freed after
it is added to the list.

Unfortunately, there are no patches to this file between
next-20230109 and next-20230110, so the bug probably is
not actually in this file.

> [   15.515426] Call trace:
> [   15.517863] Insufficient stack space to handle exception!
> [   15.517867] ESR: 0x0000000096000047 -- DABT (current EL)
> [   15.517871] FAR: 0xffff80000a047ff0
> [   15.517873] Task stack:     [0xffff80000a048000..0xffff80000a04c000]
> [   15.517877] IRQ stack:      [0xffff800008008000..0xffff80000800c000]
> [   15.517880] Overflow stack: [0xffff00007d9c1320..0xffff00007d9c2320]
> [   15.517884] CPU: 1 PID: 9 Comm: kworker/u8:0 Not tainted
> 6.2.0-rc3-next-20230110 #1
> [   15.517890] Hardware name: Libre Computer AML-S905X-CC (DT)
> [   15.517895] Workqueue: events_unbound deferred_probe_work_func
> [   15.517915] pstate: 800003c5 (Nzcv DAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   15.517923] pc : el1_abort+0x4/0x5c
> [   15.517932] lr : el1h_64_sync_handler+0x60/0xac
> [   15.517939] sp : ffff80000a048020

Not sure about the missing stack trace: I can see that the stack
pointer is on a task stack, which is reported as having overflown,
but I don't see why it's unable to print the stack while running
from the overflow stack.

A stack overflow is often caused by unbounded recursion, which
can happen when a device driver binds itself to a device that it
has just created. The log does look a bit suspicious here,
with multiple registrations for c883a000.hdmi-tx:

  986 08:02:56.487871  [   15.141218] meson-drm d0100000.vpu: Queued 2 outputs on vpu
  987 08:02:56.493572  [   15.141615] meson8b-dwmac c9410000.ethernet: Ring mode enabled
  988 08:02:56.504769  [   15.150744] meson-drm d0100000.vpu: bound c883a000.hdmi-tx (ops meson_dw_hdmi_ops [meson_dw_hdmi])
  989 08:02:56.515743  [   15.154970] meson8b-dwmac c9410000.ethernet: Enable RX Mitigation via HW Watchdog Timer
  990 08:02:56.521531  [   15.159175] lima d00c0000.gpu: pp0 - mali450 version major 0 minor 0
  991 08:02:56.526718  [   15.161436] meson-drm d0100000.vpu: Failed to find HDMI transceiver bridge
  992 08:02:56.532417  [   15.168933] lima d00c0000.gpu: pp1 - mali450 version major 0 minor 0
  993 08:02:56.537747  [   15.206102] meson-drm d0100000.vpu: Queued 2 outputs on vpu
  994 08:02:56.543435  [   15.209608] lima d00c0000.gpu: pp2 - mali450 version major 0 minor 0
  995 08:02:56.554307  [   15.217027] meson-drm d0100000.vpu: bound c883a000.hdmi-tx (ops meson_dw_hdmi_ops [meson_dw_hdmi])
  996 08:02:56.559929  [   15.221169] lima d00c0000.gpu: l2 cache 8K, 4-way, 64byte cache line, 128bit external bus
  997 08:02:56.565229  [   15.231561] meson-drm d0100000.vpu: Failed to find HDMI transceiver bridge
  998 08:02:56.576490  [   15.238133] lima d00c0000.gpu: l2 cache 64K, 4-way, 64byte cache line, 128bit external bus
  999 08:02:56.581759  [   15.253879] lima d00c0000.gpu: bus rate = 166666667
 1000 08:02:56.587248  [   15.257128] lima d00c0000.gpu: mod rate = 24000000
 1001 08:02:56.593344  [   15.261862] lima d00c0000.gpu: error -ENODEV: _opp_set_regulators: no regulator (mali) found
 1002 08:02:56.612809  [   15.286143] [drm] Initialized lima 1.1.0 20191231 for d00c0000.gpu on minor 1
 1003 08:02:56.618428  [   15.292259] meson-drm d0100000.vpu: Queued 2 outputs on vpu
 1004 08:02:56.623866  [   15.293715] meson-drm d0100000.vpu: bound c883a000.hdmi-tx (ops meson_dw_hdmi_ops [meson_dw_hdmi])
 1005 08:02:56.634771  [   15.302140] Unable to handle kernel paging request at virtual address fffffffffffffff8

Again, I don't see any recent changes in that driver or the
corresponding dts file.

      Arnd