Panic on sysfs read

[Max]

1) root@fry:~# lsb_release -rd
Description: Ubuntu 20.10
Release: 20.10

2) root@fry:~# apt-cache policy linux-image-raspi
linux-image-raspi:
  Installed: 5.8.0.1011.14
[...]

3) Nothing

4) On a Raspberry Pi 4 Rev 1.4 8GB, the kernel panics if you read the /sys/kernel/debug/regmap/dummy-avs-monitor@7d5d2000/registers file. You find a screenshot attached. Unfortunately, I don't have a serial adaptor at hand, and I didn't get netconsole working right now.

ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: linux-image-raspi 5.8.0.1011.14
ProcVersionSignature: Ubuntu 5.8.0-1011.14-raspi 5.8.18
Uname: Linux 5.8.0-1011-raspi aarch64
AlsaVersion: Advanced Linux Sound Architecture Driver Version k5.8.0-1011-raspi.
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.11-0ubuntu50.3
Architecture: arm64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path', '/dev/snd/controlC1', '/dev/snd/pcmC1D0p', '/dev/snd/controlC0', '/dev/snd/pcmC0D0p', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
Card1.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
Card1.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
CasperMD5CheckResult: skip
Date: Fri Jan 22 11:29:32 2021
ImageMediaBuild: 20201022
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lspci-vt: -[0000:00]---00.0-[01]----00.0 VIA Technologies, Inc. VL805 USB 3.0 Host Controller
Lsusb:
 Bus 002 Device 002: ID 0781:558c SanDisk Corp. Extreme Portable SSD
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 003: ID 046d:c31d Logitech, Inc. Media Keyboard K200
 Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
PciMultimedia:

ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
ProcFB: 0 BCM2708 FB
ProcKernelCmdLine: coherent_pool=1M 8250.nr_uarts=1 snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 snd_bcm2835.enable_headphones=1 bcm2708_fb.fbwidth=1920 bcm2708_fb.fbheight=1080 bcm2708_fb.fbswap=1 smsc95xx.macaddr=DC:A6:32:E2:2A:BE vc_mem.mem_base=0x3eb00000 vc_mem.mem_size=0x3ff00000 dwc_otg.lpm_enable=0 console=ttyS0,115200 console=tty1 root=LABEL=writable rootfstype=ext4 elevator=deadline rootwait fixrtc quiet splash
RelatedPackageVersions:
 linux-restricted-modules-5.8.0-1011-raspi N/A
 linux-backports-modules-5.8.0-1011-raspi N/A
 linux-firmware 1.190.3
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux-raspi
StagingDrivers: bcm2835_v4l2 bcm2835_mmal_vchiq bcm2835_codec bcm2835_isp snd_bcm2835 vc_sm_cma
UpgradeStatus: No upgrade log present (probably fresh install)
acpidump:

[Max (maxried)]

Still affects 5.8.0-1013-raspi

[Juerg Haefliger (juergh)]

[ 78.451779] 8<--- cut here ---
[ 78.454889] Unhandled fault: asynchronous external abort (0x1211) at 0x00000000
[ 78.462313] pgd = 908cc3e1
[ 78.465058] [00000000] *pgd=06cd6003, *pmd=00000000
[ 78.470014] Internal error: : 1211 [#1] PREEMPT SMP ARM
[ 78.475315] Modules linked in: dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua btsdio bluetooth ecdh_generic ecc bcm2835_codec(CE) bcm2835_isp(CE) brcmfmac bcm2835_v4l2(CE) bcm2835_mmal_vchiq(CE) v4l2_mem2mem videobuf2_dma_contig videobuf2_vmalloc videobuf2_memops brcmutil videobuf2_v4l2 videobuf2_common cfg80211 snd_bcm2835(CE) videodev snd_pcm snd_timer raspberrypi_hwmon mc snd vc_sm_cma(CE) bcm2835_gpiomem rpivid_mem uio_pdrv_genirq uio sch_fq_codel drm ip_tables x_tables autofs4 btrfs blake2b_generic raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor xor_neon raid6_pq libcrc32c raid1 raid0 multipath linear crc32_arm_ce spidev xhci_pci xhci_pci_renesas phy_generic aes_arm_bs crypto_simd cryptd
[ 78.540823] CPU: 1 PID: 1975 Comm: cat Tainted: G C E 5.11.0-1001-raspi #1
[ 78.548945] Hardware name: BCM2711
[ 78.552392] PC is at regmap_mmio_read32le+0x24/0x28
[ 78.557344] LR is at regmap_mmio_read+0x48/0x64
[ 78.561939] pc : [<c08e6664>] lr : [<c08e6838>] psr: 200f0093
[ 78.568296] sp : c80f7d88 ip : c80f7d98 fp : c80f7d94
[ 78.573594] r10: 00000014 r9 : c8180000 r8 : c80f7f68
[ 78.578892] r7 : c80f7e44 r6 : c80f7e44 r5 : 00000014 r4 : c5065680
[ 78.585515] r3 : f1061014 r2 : c80f7e44 r1 : 00000014 r0 : 00000000
[ 78.592139] Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user
[ 78.599469] Control: 30c5383d Table: 06e3aa00 DAC: 55555555
[ 78.605298] Process cat (pid: 1975, stack limit = 0xe4dc88d8)
[ 78.611127] Stack: (0xc80f7d88 to 0xc80f8000)
[ 78.615546] 7d80: c80f7db4 c80f7d98 c08e6838 c08e664c c5013e00 00000014
[ 78.623845] 7da0: c5013e00 c80f7e44 c80f7dc4 c80f7db8 c08db9f0 c08e67fc c80f7df4 c80f7dc8
[ 78.632144] 7dc0: c08df3d0 c08db9d8 00000008 c5013e00 00000014 c80f7e44 00000014 c80f7f68
[ 78.640444] 7de0: c8180000 00000014 c80f7e14 c80f7df8 c08df538 c08df36c 0000004b c5013e00
[ 78.648744] 7e00: 00000014 00000014 c80f7e84 c80f7e18 c08e5188 c08df4f8 00000014 c1189598
[ 78.657044] 7e20: 00000004 b6a5e000 c111a22c c111a224 00000000 000001fc 00020000 c140a088
[ 78.665344] 7e40: ffeee000 00000000 00000046 00000000 ffffe000 c140a088 c80f7f68 b6a5e000
[ 78.673644] 7e60: c7ac6000 b6a5e000 00020000 c49917f8 c80f7f68 c061f614 c80f7ea4 c80f7e88
[ 78.681944] 7e80: c08e54a8 c08e4ff0 00020000 c80f7f68 b6a5e000 c08e546c c80f7ecc c80f7ea8
[ 78.690243] 7ea0: c061f678 c08e5478 00020000 00000000 c7ac6000 ffffe000 b6a5e000 c80f7f68
[ 78.698543] 7ec0: c80f7f64 c80f7ed0 c0489f10 c061f620 b6a5d000 c742ada8 c6e3aa10 00000000
[ 78.706843] 7ee0: 00000000 00000001 00000000 00000000 ffeee2e8 e933e1b8 00000000 c0d7e030
[ 78.715143] 7f00: c80f7f2c c140a088 c80f7fb0 c140a088 c80f7fb0 00000a07 b6a5d000 eeecce00
[ 78.723442] 7f20: c80f7f74 c80f7f30 c0d7e030 c0290594 00000000 c140a088 c80f7f90 c7ac6000
[ 78.731741] 7f40: c7ac6000 00000000 00000000 c0200204 c80f6000...

[Juerg Haefliger (juergh)]

ATM, upstream's take on this is to leave it as is since debugfs is a 'best effort only, no guarantees' kind of thing.

https://lore.kernel.org/linux-pm/20210210114829.2915de78@gollum/

[Max (maxried)]

Ah, that's a shame... Thank you for your efforts, though. I'm unsure whether this can be exploited, but in the end, you have to be root to trigger it, right? And the Raspberry Pi's Watchdog can help you get out of this situation.

Unfortunately, you can trigger it by accident when grepping through the whole file system.

[Brian Murray (brian-murray)]

The Groovy Gorilla has reached end of life, so this bug will not be fixed for that release

[Max (maxried)]

Still happens on jammy 5.15.0-1004-raspi