Also able to crash current Oracular amd64 generic kernel with stress-ng
apparmor stressor, see attached image
** Attachment added: "image of oracular crash"
https://bugs.launchpad.net/ubuntu-realtime/+bug/2068602/+attachment/5810324/+files/Screenshot%20from%202024-08-29%2010-27-09.png
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You
With realtime access enabled via Ubuntu Pro (either via `sudo pro enable
realtime-kernel` or `sudo pro enable realtime-kernel --access-only`),
you can run the following command to download the source:
sudo apt-get source --only-source linux-realtime
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Fair point. Where can I find the source?
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https://bugs.launchpad.net/bugs/2068602
Title:
kernel oops in aafs_create in 6.8.1-1002-realtime kernel
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> Normally I'd help debug this further, but I don't know how to get
access to the RT kernel source.
You should ask for it, it'd be interesting to see what happens...
Canonical has to provide it or they're violating he GPL (I think). Maybe
file a bug here https://launchpad.net/ubuntu-realtime
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Given it's a case of adding debug into the calling paths of
aafs_create() and into aafs_create to see why the ptr is null I don't
think finding reproducers is necessary the fast path to solving this. I
suspect this is a race condition hence it's not easily reproducible in
some configurations.
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I disassembled the offending code, the error is in the following code:
r13 is zero so the mov 0x40 is accessing data from the NULL ptr in r13
8172898f: 4d 8b 55 40 mov0x40(%r13),%r10 <
here
81728993: 4d 8d ba c0 00 00 00lea0xc0(%r10),%r1
To be clear, so far I've only been able to get the following hardware
configurations to fail reliably:
- QEMU VM amd64, linux-realtime 6.8.1-1002-realtime
- QEMU VM amd64, linux (generic) 6.8.0-35-generic
I once got each of the following to fail, but haven't been able to
reproduce it consistently
Hi Colin, I've been able to reproduce this issue in QEMU VMs on amd64
consistently and I got it to happen once in arm64, however, I haven't
been able to reproduce the kernel oops again. I can't get it to happen
on bare metal or in an LXD VM (multipass). I've also found that this
doesn't just happen
** Package changed: linux (Ubuntu) => linux-realtime (Ubuntu)
** Package changed: linux-realtime (Ubuntu) => ubuntu-realtime
** Changed in: ubuntu-realtime
Importance: Medium => High
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Same issue on ARM64 with 6.8.1-1002-realtime too:
stress-ng: error: [4568] klog-check: alert: [445.413206] 'Unable to handle
kernel access to user memory outside uaccess routines at virtual address
0040'
stress-ng: error: [4568] klog-check: alert: [445.413235] 'Mem abort info:'
stres
** Summary changed:
- kernel oops in aafs_create in 6.8.1-1002-realtime
+ kernel oops in aafs_create in 6.8.1-1002-realtime kernel
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Title:
kerne
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