Re: CVE-2025-38026: x86/sev: Do not touch VMSA pages during SNP guest memory kdump

Re: CVE-2025-38026: x86/sev: Do not touch VMSA pages during SNP guest memory kdump

[Juergen Gross]

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On 18.06.25 11:29, Greg Kroah-Hartman wrote:
> From: Greg Kroah-Hartman <gregkh@kernel.org>
> 
> Description
> ===========
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> x86/sev: Do not touch VMSA pages during SNP guest memory kdump
> 
> When kdump is running makedumpfile to generate vmcore and dump SNP guest
> memory it touches the VMSA page of the vCPU executing kdump.
> 
> It then results in unrecoverable #NPF/RMP faults as the VMSA page is
> marked busy/in-use when the vCPU is running and subsequently a causes
> guest softlockup/hang.
> 
> Additionally, other APs may be halted in guest mode and their VMSA pages
> are marked busy and touching these VMSA pages during guest memory dump
> will also cause #NPF.
> 
> Issue AP_DESTROY GHCB calls on other APs to ensure they are kicked out
> of guest mode and then clear the VMSA bit on their VMSA pages.
> 
> If the vCPU running kdump is an AP, mark it's VMSA page as offline to
> ensure that makedumpfile excludes that page while dumping guest memory.
> 
> The Linux kernel CVE team has assigned CVE-2025-38026 to this issue.

I don't see how this issue could be triggered by an unprivileged user.
I think this CVE should be revoked.


Juergen

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Re: CVE-2025-38026: x86/sev: Do not touch VMSA pages during SNP guest memory kdump

[Greg KH]

On Wed, Jun 18, 2025 at 11:57:22AM +0200, Juergen Gross wrote:
> On 18.06.25 11:29, Greg Kroah-Hartman wrote:
> > From: Greg Kroah-Hartman <gregkh@kernel.org>
> > 
> > Description
> > ===========
> > 
> > In the Linux kernel, the following vulnerability has been resolved:
> > 
> > x86/sev: Do not touch VMSA pages during SNP guest memory kdump
> > 
> > When kdump is running makedumpfile to generate vmcore and dump SNP guest
> > memory it touches the VMSA page of the vCPU executing kdump.
> > 
> > It then results in unrecoverable #NPF/RMP faults as the VMSA page is
> > marked busy/in-use when the vCPU is running and subsequently a causes
> > guest softlockup/hang.
> > 
> > Additionally, other APs may be halted in guest mode and their VMSA pages
> > are marked busy and touching these VMSA pages during guest memory dump
> > will also cause #NPF.
> > 
> > Issue AP_DESTROY GHCB calls on other APs to ensure they are kicked out
> > of guest mode and then clear the VMSA bit on their VMSA pages.
> > 
> > If the vCPU running kdump is an AP, mark it's VMSA page as offline to
> > ensure that makedumpfile excludes that page while dumping guest memory.
> > 
> > The Linux kernel CVE team has assigned CVE-2025-38026 to this issue.
> 
> I don't see how this issue could be triggered by an unprivileged user.
> I think this CVE should be revoked.

Now rejected, thanks for the review.

greg k-h