Messages in this thread | | | Date | Sun, 11 Aug 2019 17:33:26 +0200 | From | Salvatore Bonaccorso <> | Subject | Re: [Linux 5.2.x] /sys/kernel/debug/tracing/events/power/cpu_idle/id: BUG: kernel NULL pointer dereference, address: 0000000000000000 |
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Thomas,
On Sun, Aug 11, 2019 at 02:58:15PM +0200, Thomas Gleixner wrote: > Salvatore, > > On Sun, 11 Aug 2019, Salvatore Bonaccorso wrote: > > On Sun, Aug 11, 2019 at 08:22:35AM +0200, Thomas Gleixner wrote: > > > On Sat, 10 Aug 2019, Paul Menzel wrote: > > > > For the record. It is also reproducible with Linux 5.2.6, and trying to print > > > > the file contents with cat already fails. > > > > > > > > ``` > > > > $ sudo ls -l /sys/kernel/debug/tracing/events/power/cpu_idle/id > > > > -r--r--r-- 1 root root 0 Aug 10 23:05 > > > > /sys/kernel/debug/tracing/events/power/cpu_idle/id > > > > $ sudo cat /sys/kernel/debug/tracing/events/power/cpu_idle/id > > > > Killed > > > > ``` > > > > This seems to be related to https://bugs.debian.org/934304 (in > > particular https://bugs.debian.org/934304#29). The mentioned patch > > features/all/lockdown/0031-tracefs-Restrict-tracefs-when-the-kernel-is-locked-d.patch > > is a backport of https://patchwork.kernel.org/patch/11069661/ with > > only change that it is converted back to the non-LSM lockdown API. > > So that's a debian kernel specific issue?
"yes". A kernel build without the above patch does not exhibit the issue. So the issue is specific to that lockdown patch ("tracefs: Restrict tracefs when the kernel is locked down").
Steven and Matthew are both CC'ed.
Regards, Salvatore
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