Requesting stable merge for commit 1978b3a53a74e3230cd46932b149c6e62e832e9a

Requesting stable merge for commit 1978b3a53a74e3230cd46932b149c6e62e832e9a

[Anand K. Mistry]

Hi,

I'm requesting a stable merge for commit
1978b3a53a74e3230cd46932b149c6e62e832e9a
("x86/speculation: Allow IBPB to be conditionally enabled on CPUs with
always-on STIBP")
into the stable branch for 5.4. Note, the commit is already queued for
inclusion into the next 5.9 stable release
(https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/queue-5.9/x86-speculation-allow-ibpb-to-be-conditionally-enabl.patch).

The patch fixes an issue where a Spectre-v2-user mitigation could not
be enabled via prctl() on certain AMD CPUs. The issue was introduced
in commit 21998a351512eba4ed5969006f0c55882d995ada
("x86/speculation: Avoid force-disabling IBPB based on STIBP and
enhanced IBRS.")
which was merged into the 5.4 stable branch as commit
6d60d5462a91eb46fb88b016508edfa8ee0bc7c8. This commit also exists in
4.19, 4.14, 4.9, and 4.4, so those kernels are also likely affected by
this bug.


-- 
Anand K. Mistry
Software Engineer
Google Australia

Re: Requesting stable merge for commit 1978b3a53a74e3230cd46932b149c6e62e832e9a

[Greg KH]

On Wed, Nov 11, 2020 at 11:09:13PM +1100, Anand K. Mistry wrote:
> Hi,
> 
> I'm requesting a stable merge for commit
> 1978b3a53a74e3230cd46932b149c6e62e832e9a
> ("x86/speculation: Allow IBPB to be conditionally enabled on CPUs with
> always-on STIBP")
> into the stable branch for 5.4. Note, the commit is already queued for
> inclusion into the next 5.9 stable release
> (https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/queue-5.9/x86-speculation-allow-ibpb-to-be-conditionally-enabl.patch).
> 
> The patch fixes an issue where a Spectre-v2-user mitigation could not
> be enabled via prctl() on certain AMD CPUs. The issue was introduced
> in commit 21998a351512eba4ed5969006f0c55882d995ada
> ("x86/speculation: Avoid force-disabling IBPB based on STIBP and
> enhanced IBRS.")
> which was merged into the 5.4 stable branch as commit
> 6d60d5462a91eb46fb88b016508edfa8ee0bc7c8. This commit also exists in
> 4.19, 4.14, 4.9, and 4.4, so those kernels are also likely affected by
> this bug.

As I asked when I sent out a "FAILED:" message for this patch, if
someone wants it backported to older kernels, they will need to provide
the backported versions of it, as the patch does not apply cleanly
as-is.

Can you please do that?

thanks,

greg k-h

Re: Requesting stable merge for commit 1978b3a53a74e3230cd46932b149c6e62e832e9a

[Anand K. Mistry]

On Wed, 11 Nov 2020 at 23:23, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Nov 11, 2020 at 11:09:13PM +1100, Anand K. Mistry wrote:
> > Hi,
> >
> > I'm requesting a stable merge for commit
> > 1978b3a53a74e3230cd46932b149c6e62e832e9a
> > ("x86/speculation: Allow IBPB to be conditionally enabled on CPUs with
> > always-on STIBP")
> > into the stable branch for 5.4. Note, the commit is already queued for
> > inclusion into the next 5.9 stable release
> > (https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/queue-5.9/x86-speculation-allow-ibpb-to-be-conditionally-enabl.patch).
> >
> > The patch fixes an issue where a Spectre-v2-user mitigation could not
> > be enabled via prctl() on certain AMD CPUs. The issue was introduced
> > in commit 21998a351512eba4ed5969006f0c55882d995ada
> > ("x86/speculation: Avoid force-disabling IBPB based on STIBP and
> > enhanced IBRS.")
> > which was merged into the 5.4 stable branch as commit
> > 6d60d5462a91eb46fb88b016508edfa8ee0bc7c8. This commit also exists in
> > 4.19, 4.14, 4.9, and 4.4, so those kernels are also likely affected by
> > this bug.
>
> As I asked when I sent out a "FAILED:" message for this patch, if
> someone wants it backported to older kernels, they will need to provide
> the backported versions of it, as the patch does not apply cleanly
> as-is.
>
> Can you please do that?

Oh, I didn't get that message. I'll prepare a backport.

>
> thanks,
>
> greg k-h



-- 
Anand K. Mistry
Software Engineer
Google Australia

Re: Requesting stable merge for commit 1978b3a53a74e3230cd46932b149c6e62e832e9a

[Greg KH]

On Thu, Nov 12, 2020 at 10:12:01AM +1100, Anand K. Mistry wrote:
> On Wed, 11 Nov 2020 at 23:23, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Wed, Nov 11, 2020 at 11:09:13PM +1100, Anand K. Mistry wrote:
> > > Hi,
> > >
> > > I'm requesting a stable merge for commit
> > > 1978b3a53a74e3230cd46932b149c6e62e832e9a
> > > ("x86/speculation: Allow IBPB to be conditionally enabled on CPUs with
> > > always-on STIBP")
> > > into the stable branch for 5.4. Note, the commit is already queued for
> > > inclusion into the next 5.9 stable release
> > > (https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/queue-5.9/x86-speculation-allow-ibpb-to-be-conditionally-enabl.patch).
> > >
> > > The patch fixes an issue where a Spectre-v2-user mitigation could not
> > > be enabled via prctl() on certain AMD CPUs. The issue was introduced
> > > in commit 21998a351512eba4ed5969006f0c55882d995ada
> > > ("x86/speculation: Avoid force-disabling IBPB based on STIBP and
> > > enhanced IBRS.")
> > > which was merged into the 5.4 stable branch as commit
> > > 6d60d5462a91eb46fb88b016508edfa8ee0bc7c8. This commit also exists in
> > > 4.19, 4.14, 4.9, and 4.4, so those kernels are also likely affected by
> > > this bug.
> >
> > As I asked when I sent out a "FAILED:" message for this patch, if
> > someone wants it backported to older kernels, they will need to provide
> > the backported versions of it, as the patch does not apply cleanly
> > as-is.
> >
> > Can you please do that?
> 
> Oh, I didn't get that message. I'll prepare a backport.

You didn't have to get the email, but I would assume that you at least
tested the backport if you asked for it to happen, right?  :)

thanks,

greg k-h

Re: Requesting stable merge for commit 1978b3a53a74e3230cd46932b149c6e62e832e9a

[Anand K. Mistry]

On Thu, 12 Nov 2020 at 17:15, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Thu, Nov 12, 2020 at 10:12:01AM +1100, Anand K. Mistry wrote:
> > On Wed, 11 Nov 2020 at 23:23, Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Wed, Nov 11, 2020 at 11:09:13PM +1100, Anand K. Mistry wrote:
> > > > Hi,
> > > >
> > > > I'm requesting a stable merge for commit
> > > > 1978b3a53a74e3230cd46932b149c6e62e832e9a
> > > > ("x86/speculation: Allow IBPB to be conditionally enabled on CPUs with
> > > > always-on STIBP")
> > > > into the stable branch for 5.4. Note, the commit is already queued for
> > > > inclusion into the next 5.9 stable release
> > > > (https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/queue-5.9/x86-speculation-allow-ibpb-to-be-conditionally-enabl.patch).
> > > >
> > > > The patch fixes an issue where a Spectre-v2-user mitigation could not
> > > > be enabled via prctl() on certain AMD CPUs. The issue was introduced
> > > > in commit 21998a351512eba4ed5969006f0c55882d995ada
> > > > ("x86/speculation: Avoid force-disabling IBPB based on STIBP and
> > > > enhanced IBRS.")
> > > > which was merged into the 5.4 stable branch as commit
> > > > 6d60d5462a91eb46fb88b016508edfa8ee0bc7c8. This commit also exists in
> > > > 4.19, 4.14, 4.9, and 4.4, so those kernels are also likely affected by
> > > > this bug.
> > >
> > > As I asked when I sent out a "FAILED:" message for this patch, if
> > > someone wants it backported to older kernels, they will need to provide
> > > the backported versions of it, as the patch does not apply cleanly
> > > as-is.
> > >
> > > Can you please do that?
> >
> > Oh, I didn't get that message. I'll prepare a backport.
>
> You didn't have to get the email, but I would assume that you at least
> tested the backport if you asked for it to happen, right?  :)

The conflict was so trivial (a single newline in a comment) I didn't
really think about it. And yes, the patch is well tested against 5.4
(which is my target kernel), and 4.14.