kernel with kasan compiled in fails to boot

[miroR]

early console in decompress_kernel
input_data: 0x0000000002eb324d
input_len: 0x00000000000165d8
output: 0x0000000001000000
output_len: 0x00000000026d6b20
run_size: 0x0000000002a00000

Decompressing Linux... Parsing ELF... done.
Booting the kernel.
_

(where the last line, consisting of one char, namely '_', ominously blinks...
forever)

I tried with and without modules, in all variants (ah, just remembered, haven't tried vanilla kernels yet). But invariably it does not boot.
To see more about my system, pls look up the Gentoo Bugzilla, lots of info on my system there:
https://bugs.gentoo.org/show_bug.cgi?id=597554
such as:
https://bugs.gentoo.org/attachment.cgi?id=451298

[dvyukov]

Hi,

There are no known issues with booting KASAN kernels. All configurations we tried work.

Please provide:

• commit hash/tree
• compiler version
• config (the one you referenced contains # CONFIG_KASAN is not set)
• how you boot it (e.g. qemu command line)

[miroR]

• commit hash/tree
  (I don't understand that, I know the words, but I just set kasan option on in the kernel
• compiler version
  is around these settings:
  https://597554.bugs.gentoo.org/attachment.cgi?id=451296
  ( ... gcc-5.4.0 ....), it's in that Gentoo bug report
• config (the one you referenced contains # CONFIG_KASAN is not set)
  You mean in this one:
  https://bugs.gentoo.org/attachment.cgi?id=451298
  True, what I meant was, onto such kernel config I added KASAN option.

The diff btwn that one and a KASAN enabled option one is (open attached file pls):
Kasan_161029_diff.txt

BTW. this: https://lkml.org/lkml/2016/6/21/541 seems to be of your writing. Appears to be the same issue in that Gentoo Bugzilla I gave links to ...

[dvyukov]

commit hash/tree (I don't understand that, I know the words, but I just set kasan option on in the kernel

How did you obtain kernel sources?
If it is git checkout, then provide output of git remote -v, git branch and git rev-parse HEAD commands.

Also, how you boot it (e.g. qemu command line)?

[miroR]

No, not from git. It is a regular hardened-sources Gentoo package:
https://packages.gentoo.org/packages/sys-kernel/hardened-sources
Also, while the bug I gave link to is about libvirt and qemu getting crashed
(
the cause actually likely some use-after-free condition according to PaX Team:
https://bugs.gentoo.org/show_bug.cgi?id=597554#c16
)...
[while the bug is about libvirt and qemu], I got that message on top with the ominous "" blinking forever with regular kernel install, not in VM, and regular booting.
And I can confirm that just adding those same KASAN option into the config file such as the one linked in this issue further above, only with the latest hardened-sources, which is:
4.7.10-r1
also stalls the booting at the ominous "" as explained on top.
Removing the KASAN options from the .config of 4.7.10-r1 kernel and recompiling, and it boots fine.
What itches me, is, like you wrote:
"The following program triggers use-after-free in kvm_irqfd_release: ..."
so what itches me is what is it that triggers "use-after-free in kvm_irqfd_release:" in my machines?
if I suspect correctly here...

[miroR]

I meant, like you wrote:
"The following program triggers use-after-free in kvm_irqfd_release: ..."
in:
https://lkml.org/lkml/2016/6/21/541

[dvyukov]

What I am looking for is step-by-step reproduction instructions, namely a sequence of commands that can copy-paste into my console to reproduce the issue. I can't debug if I can't reproduce it.
Or you can debug and fix it yourself. As I said there are no similar known issues, so I can't help straight away.

[xairy]

Closing, please reopen if the issue persists.