Re: [PATCH 5.5 000/176] 5.5.8-stable review

Greg Kroah-Hartman
2020-03-04T11:52:37Z

On Wed, Mar 04, 2020 at 04:22:30PM +0530, Naresh Kamboju wrote:
> On Wed, 4 Mar 2020 at 14:19, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Wed, Mar 04, 2020 at 09:47:02AM +0100, Greg Kroah-Hartman wrote:
> > > On Wed, Mar 04, 2020 at 09:11:28AM +0100, Greg Kroah-Hartman wrote:
> > > > On Wed, Mar 04, 2020 at 12:43:42PM +0530, Naresh Kamboju wrote:
> > > > > On Tue, 3 Mar 2020 at 23:16, Greg Kroah-Hartman
> > > > > <gregkh@linuxfoundation.org> wrote:
> > > > > >
> > > > > > This is the start of the stable review cycle for the 5.5.8 release.
> > > > > > There are 176 patches in this series, all will be posted as a response
> > > > > > to this one. If anyone has any issues with these being applied, please
> > > > > > let me know.
> > > > > >
> > > > > > Responses should be made by Thu, 05 Mar 2020 17:42:06 +0000.
> > > > > > Anything received after that time might be too late.
> > > > > >
> > > > > > The whole patch series can be found in one patch at:
> > > > > > https://www.kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.5.8-rc1.gz
> > > > > > or in the git tree and branch at:
> > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.5.y
> > > > > > and the diffstat can be found below.
> > > > > >
> > > > > > thanks,
> > > > > >
> > > > > > greg k-h
> > > > > >
> > > > >
> > > > > Results from Linaro’s test farm.
> > > > > Regressions detected on x86_64 and i386.
> > > > >
> > > > > Test failure output:
> > > > > CVE-2017-5715: VULN (IBRS+IBPB or retpoline+IBPB+RSB filling, is
> > > > > needed to mitigate the vulnerability)
> > > > >
> > > > > Test description:
> > > > > CVE-2017-5715 branch target injection (Spectre Variant 2)
> > > > >
> > > > > Impact: Kernel
> > > > > Mitigation 1: new opcode via microcode update that should be used by
> > > > > up to date compilers to protect the BTB (by flushing indirect branch
> > > > > predictors)
> > > > > Mitigation 2: introducing "retpoline" into compilers, and recompile
> > > > > software/OS with it
> > > > > Performance impact of the mitigation: high for mitigation 1, medium
> > > > > for mitigation 2, depending on your CPU
> > > >
> > > > So these are regressions or just new tests?
> > > >
> > > > If regressions, can you do 'git bisect' to find the offending commit?
> > > >
> > > > Also, are you sure you have an updated microcode on these machines and a
> > > > proper compiler for retpoline?
> > >
> > > As an example of just how crazy that script is, here's the output of my
> > > machine for that first CVE issue:
> > >
> > > CVE-2017-5715 aka 'Spectre Variant 2, branch target injection'
> > > * Mitigated according to the /sys interface: YES (Mitigation: Full generic retpoline, IBPB: conditional, IBRS_FW, STIBP: conditional, RSB filling)
> > > * Mitigation 1
> > > * Kernel is compiled with IBRS support: YES
> > > * IBRS enabled and active: YES (for firmware code only)
> > > * Kernel is compiled with IBPB support: YES
> > > * IBPB enabled and active: YES
> > > * Mitigation 2
> > > * Kernel has branch predictor hardening (arm): NO
> > > * Kernel compiled with retpoline option: YES
> > > * Kernel compiled with a retpoline-aware compiler: YES (kernel reports full retpoline compilation)
> > > * Kernel supports RSB filling: UNKNOWN (couldn't check (couldn't find your kernel image in /boot, if you used netboot, this is normal))
> > > > STATUS: VULNERABLE (IBRS+IBPB or retpoline+IBPB+RSB filling, is needed to mitigate
> > >
> > > So why is this "Vulnerable"? Because it didn't think it could find my
> > > kernel image for some odd reason, despite it really being in /boot/ (I
> > > don't use netboot)
>
> Now I know the real reason why this test failed.
> With this note we can conclude this is not a regression.
>
> No regressions on arm64, arm, x86_64, and i386 for 4.19, 5.4 and 5.5 branches.

Great, thanks for confirming and for testing all of these.

greg k-h