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Message-ID: <CAAH4kHba3yFuohazDHGXYDwymKhUkHeSRq2hpaoPOvYBs6tu5g@mail.gmail.com>
Date: Wed, 6 Nov 2024 07:30:27 -0800
From: Dionna Amalie Glaze <dionnaglaze@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>, Michael Roth <michael.roth@....com>,
Brijesh Singh <brijesh.singh@....com>, Ashish Kalra <ashish.kalra@....com>,
Tom Lendacky <thomas.lendacky@....com>, John Allen <john.allen@....com>,
Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>,
Luis Chamberlain <mcgrof@...nel.org>, Russ Weight <russ.weight@...ux.dev>,
Danilo Krummrich <dakr@...hat.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>, Tianfei zhang <tianfei.zhang@...el.com>,
Alexey Kardashevskiy <aik@....com>, kvm@...r.kernel.org
Subject: Re: [PATCH v4 1/6] kvm: svm: Fix gctx page leak on invalid inputs
On Wed, Nov 6, 2024 at 6:34 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> KVM: SVM:
>
> In the future, please post bug fixes separately from new features series, especially
> when the fix has very little to do with the rest of the series (AFAICT, this has
> no relation whatsoever beyond SNP).
>
Understood. Are dependent series best shared through links to a dev
branch containing all patches?
> On Tue, Nov 05, 2024, Dionna Glaze wrote:
> > Ensure that snp gctx page allocation is adequately deallocated on
> > failure during snp_launch_start.
> >
> > Fixes: 136d8bc931c8 ("KVM: SEV: Add KVM_SEV_SNP_LAUNCH_START command")
>
> This needs
>
> Cc: stable@...r.kernel.org
>
> especially if it doesn't get into 6.12.
>
> > CC: Sean Christopherson <seanjc@...gle.com>
> > CC: Paolo Bonzini <pbonzini@...hat.com>
> > CC: Thomas Gleixner <tglx@...utronix.de>
> > CC: Ingo Molnar <mingo@...hat.com>
> > CC: Borislav Petkov <bp@...en8.de>
> > CC: Dave Hansen <dave.hansen@...ux.intel.com>
> > CC: Ashish Kalra <ashish.kalra@....com>
> > CC: Tom Lendacky <thomas.lendacky@....com>
> > CC: John Allen <john.allen@....com>
> > CC: Herbert Xu <herbert@...dor.apana.org.au>
> > CC: "David S. Miller" <davem@...emloft.net>
> > CC: Michael Roth <michael.roth@....com>
> > CC: Luis Chamberlain <mcgrof@...nel.org>
> > CC: Russ Weight <russ.weight@...ux.dev>
> > CC: Danilo Krummrich <dakr@...hat.com>
> > CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > CC: "Rafael J. Wysocki" <rafael@...nel.org>
> > CC: Tianfei zhang <tianfei.zhang@...el.com>
> > CC: Alexey Kardashevskiy <aik@....com>
> >
> > Signed-off-by: Dionna Glaze <dionnaglaze@...gle.com>
>
> Acked-by: Sean Christopherson <seanjc@...gle.com>
>
> Paolo, do you want to grab this one for 6.12 too?
>
> > ---
> > arch/x86/kvm/svm/sev.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index 714c517dd4b72..f6e96ec0a5caa 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -2212,10 +2212,6 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
> > if (sev->snp_context)
> > return -EINVAL;
> >
> > - sev->snp_context = snp_context_create(kvm, argp);
> > - if (!sev->snp_context)
> > - return -ENOTTY;
> > -
> > if (params.flags)
> > return -EINVAL;
> >
> > @@ -2230,6 +2226,10 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
> > if (params.policy & SNP_POLICY_MASK_SINGLE_SOCKET)
> > return -EINVAL;
> >
> > + sev->snp_context = snp_context_create(kvm, argp);
> > + if (!sev->snp_context)
> > + return -ENOTTY;
>
> Related to this fix, the return values from snp_context_create() are garbage. It
> should return ERR_PTR(), not NULL. -ENOTTY on an OOM scenatio is blatantly wrong,
> as -ENOTTY on any SEV_CMD_SNP_GCTX_CREATE failure is too.
>
I caught this too. I'll be changing that behavior with the new gctx
management API from ccp in v5, i.e.,
/**
* sev_snp_create_context - allocates an SNP context firmware page
*
* Associates the created context with the ASID that an activation
* call after SNP_LAUNCH_START will commit. The association is needed
* to track active GCTX pages to refresh during firmware hotload.
*
* @asid: The ASID allocated to the caller that will be used in a
subsequent SNP_ACTIVATE.
* @psp_ret: sev command return code.
*
* Returns:
* A pointer to the SNP context page, or an ERR_PTR of
* -%ENODEV if the PSP device is not available
* -%ENOTSUPP if PSP device does not support SEV
* -%ETIMEDOUT if the SEV command timed out
* -%EIO if PSP device returned a non-zero return code
*/
void *sev_snp_create_context(int asid, int *psp_ret);
/**
* sev_snp_activate_asid - issues SNP_ACTIVATE for the asid and
associated GCTX page.
*
* @asid: The ASID to activate.
* @psp_ret: sev command return code.
*
* Returns:
* 0 if the SEV device successfully processed the command
* -%ENODEV if the PSP device is not available
* -%ENOTSUPP if PSP device does not support SEV
* -%ETIMEDOUT if the SEV command timed out
* -%EIO if PSP device returned a non-zero return code
*/
int sev_snp_activate_asid(int asid, int *psp_ret);
/**
* sev_snp_guest_decommission - issues SNP_DECOMMISSION for an asid's
GCTX page and frees it.
*
* @asid: The ASID to activate.
* @psp_ret: sev command return code.
*
* Returns:
* 0 if the SEV device successfully processed the command
* -%ENODEV if the PSP device is not available
* -%ENOTSUPP if PSP device does not support SEV
* -%ETIMEDOUT if the SEV command timed out
* -%EIO if PSP device returned a non-zero return code
*/
int sev_snp_guest_decommission(int asid, int *psp_ret);
> > +
> > start.gctx_paddr = __psp_pa(sev->snp_context);
> > start.policy = params.policy;
> > memcpy(start.gosvw, params.gosvw, sizeof(params.gosvw));
> > --
> > 2.47.0.199.ga7371fff76-goog
> >
--
-Dionna Glaze, PhD, CISSP, CCSP (she/her)
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