Comment 0 for bug 1757217

This was discovered while investigating tracebacks in the cert suite. We have a script that parses /proc/modules and returns the information in a more human-readable format as part of the info gathering we do during cert testing.

On 4.13 and older kernels, this script was run as a normal user with no error. On 4.15, this script dumps a python trace because /proc/modules now returns a null reference instead of just a blank memory offset.

On 4.13 and older, when you read the file, you get something like this (root and non-root shown)

bladernr@galactica:~$ sudo cat /proc/modules |grep nls_iso8859
nls_iso8859_1 16384 1 - Live 0xffffffffc06b5000
bladernr@galactica:~$ cat /proc/modules |grep nls_iso8859
nls_iso8859_1 16384 1 - Live 0x0000000000000000

Note that non-root reading returns a memory offset of 0x0 which is easily parsable.

ubuntu@xwing:~$ sudo cat /proc/modules |grep e1000e
e1000e 249856 0 - Live 0xffffffffc0225000
ptp 20480 2 igb,e1000e, Live 0xffffffffc00a9000
ubuntu@xwing:~$ cat /proc/modules |grep e1000e
e1000e 249856 0 - Live 0x (null)
ptp 20480 2 igb,e1000e, Live 0x (null)

Now, however, non-root reading returns a null reference which causes attempts to parse the offset to fail.

I imagine this is probably by design, and it's a minor bug, but I wanted to raise it as it could cause issues when running userspace tools that parse /proc/modules on 4.15.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-12-generic 4.15.0-12.13
ProcVersionSignature: User Name 4.15.0-12.13-generic 4.15.7
Uname: Linux 4.15.0-12-generic x86_64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Mar 20 17:24 seq
 crw-rw---- 1 root audio 116, 33 Mar 20 17:24 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord': 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Tue Mar 20 17:59:51 2018
MachineType: LENOVO INVALID
PciMultimedia:

ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-12-generic.efi.signed root=UUID=9fdf32ba-26ce-4d54-8457-dbd62057c7e9 ro
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-12-generic N/A
 linux-backports-modules-4.15.0-12-generic N/A
 linux-firmware 1.173
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/07/2017
dmi.bios.vendor: LENOVO
dmi.bios.version: FBKT97CUS
dmi.board.name: ThinkServer RS140
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.type: 7
dmi.chassis.vendor: LENOVO
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnLENOVO:bvrFBKT97CUS:bd04/07/2017:svnLENOVO:pnINVALID:pvrFFFFFFF:rvnLENOVO:rnThinkServerRS140:rvrNotDefined:cvnLENOVO:ct7:cvrToBeFilledByO.E.M.:
dmi.product.family: To be filled by O.E.M.
dmi.product.name: INVALID
dmi.product.version: FFFFFFF
dmi.sys.vendor: LENOVO