[apparmor] Bug#885775: apparmor: Apparmor triggers NULL pointer dereference in kernel 4.14.7-1 when updating with aptitude

[John Johansen]

On 12/29/2017 11:29 PM, intrigeri wrote:
> Control: forwarded -1 apparmor at lists.ubuntu.com
> 
> Hi AppArmor kernel developers,
> 
> we got this bug reported in Debian:
> 
> Kertesz Laszlo:
>>    * What led up to the situation?
>> 	Installed kernel 4.14 in Debian Testing and ever since at every upgrade where systemd or other important 
>> 	packages were upgraded the system froze with the last 2 lines in the system log:
> 
>> 	Dec 29 21:25:26 laca-desktop kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
>> 	Dec 29 21:25:26 laca-desktop kernel: IP: __task_pid_nr_ns+0xc7/0xf0
> 
>> 	The system became unresponsive, not even the sysrq combinations were working
>>    * What exactly did you do (or not do) that was effective (or
>>      ineffective)?
>> 	Restarted ran dpkg --configure -a and every time the system froze
>> 	Booting with the 4.13 kernel was fine, dpkg finished its run
> 
>> 	At the next upgrade i still got the freeze, after reboot i disabled the kernel security features with the kernel command line security=false
> 
>>    * What was the outcome of this action?
>> 	dpkg was working fine with the kernel 4.14 too
> 
> Do you need more info from me or from the bug reporter (Kertesz
> Laszlo, Cc'ed)?
> 

yes please. This really isn't enough info to debug off of. AppArmor
does not call __task_pid_nr_ns() nor even any of the fns() that call
it directly.

We need more of a call trace to even have a chance of chasing this
down.