Bug 209845

Summary:	ignore_msrs kernel NULL pointer dereference since 12bc2132b15e0a969b3f455d90a5f215ef239eff
Product:	Virtualization	Reporter:	Steffen Dirkwinkel (kernel-bugs)
Component:	kvm	Assignee:	virtualization_kvm
Status:	NEW ---
Severity:	normal
Priority:	P1
Hardware:	x86-64
OS:	Linux
Kernel Version:	5.9	Subsystem:
Regression:	Yes	Bisected commit-id:
Attachments:	dmesg section

Description Steffen Dirkwinkel 2020-10-25 11:28:21 UTC

Created attachment 293183 [details]
dmesg section

Since commit 12bc2132b15e0a969b3f455d90a5f215ef239eff kvm crashes with a null pointer dereference when ignore_msrs is set (log in attachement) 

Hardware: AMD Ryzen 3700x


other reports:
- https://www.reddit.com/r/VFIO/comments/jdh9pp/so_i_just_updated_to_kernel_591_and/ 


- https://forum.manjaro.org/t/kernel-5-9-no-virtualization/31562

Comment 1 peterx 2020-10-25 16:24:27 UTC

On Sun, Oct 25, 2020 at 11:28:21AM +0000, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=209845
> 
>             Bug ID: 209845
>            Summary: ignore_msrs kernel NULL pointer dereference since
>                     12bc2132b15e0a969b3f455d90a5f215ef239eff
>            Product: Virtualization
>            Version: unspecified
>     Kernel Version: 5.9
>           Hardware: x86-64
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: kvm
>           Assignee: virtualization_kvm@kernel-bugs.osdl.org
>           Reporter: kernel-bugs@steffen.cc
>         Regression: No
> 
> Created attachment 293183 [details]
>   --> https://bugzilla.kernel.org/attachment.cgi?id=293183&action=edit
> dmesg section
> 
> Since commit 12bc2132b15e0a969b3f455d90a5f215ef239eff kvm crashes with a null
> pointer dereference when ignore_msrs is set (log in attachement) 
> 
> Hardware: AMD Ryzen 3700x

kvm_msr_ignored_check() should consider vcpu null case for kvm vm get msr
features..  I'll post a fix soon, probably with a selftest too.  Thanks,