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From: Marc Zyngier <maz@kernel.org>
To: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Andrew Scull <ascull@google.com>, Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Quentin Perret <qperret@google.com>,
	David Brazdil <dbrazdil@google.com>,
	kernel-team@android.com
Subject: Re: [PATCH v2 11/11] KVM: arm64: Get rid of the AArch32 register mapping code
Date: Thu, 23 May 2024 17:04:05 +0100	[thread overview]
Message-ID: <86le40ms5m.wl-maz@kernel.org> (raw)
In-Reply-To: <66a7077c5df86d0a541237996382ae583d690a14.camel@linux.ibm.com>

Hi Nina,

On Thu, 23 May 2024 15:25:21 +0100,
Nina Schoetterl-Glausch <nsg@linux.ibm.com> wrote:
> 
> On Mon, 2020-11-02 at 16:40 +0000, Marc Zyngier wrote:

Wow, you're digging out the old dregs... But it is worth it!

>
> [...]
> 
> > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> > index dfb5218137ca..3f23f7478d2a 100644
> > --- a/arch/arm64/kvm/guest.c
> > +++ b/arch/arm64/kvm/guest.c
> > @@ -252,10 +252,32 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> >  	memcpy(addr, valp, KVM_REG_SIZE(reg->id));
> 
> I was looking at KVM_(G|S)ET_ONE_REG implementations and something looks off to me here:
> 
> ...
> 
> 	if (off == KVM_REG_ARM_CORE_REG(regs.pstate)) {
> 		u64 mode = (*(u64 *)valp) & PSR_AA32_MODE_MASK;
> 		switch (mode) {
> 
> Masking and switch over mode here...
> 
> 		case PSR_AA32_MODE_USR:
> 			if (!kvm_supports_32bit_el0())
> 				return -EINVAL;
> 			break;
> 		case PSR_AA32_MODE_FIQ:
> 		case PSR_AA32_MODE_IRQ:
> ...
> >  
> >  	if (*vcpu_cpsr(vcpu) & PSR_MODE32_BIT) {
> > -		int i;
> > +		int i, nr_reg;
> > +
> > +		switch (*vcpu_cpsr(vcpu)) {
> 
> ...but switching over mode without masking here.
> I don't know if this is as intended, but I thought I'd mention it.

Amazing. Thanks for spotting this. This is indeed broken. I guess this
was not spotted because userspace is not totally broken itself.

Do you want to submit a fix adding the masking back? or should I do it
myself?

Thanks again,

	M.

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Andrew Scull <ascull@google.com>, Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Quentin Perret <qperret@google.com>,
	David Brazdil <dbrazdil@google.com>,
	kernel-team@android.com
Subject: Re: [PATCH v2 11/11] KVM: arm64: Get rid of the AArch32 register mapping code
Date: Thu, 23 May 2024 17:04:05 +0100	[thread overview]
Message-ID: <86le40ms5m.wl-maz@kernel.org> (raw)
In-Reply-To: <66a7077c5df86d0a541237996382ae583d690a14.camel@linux.ibm.com>

Hi Nina,

On Thu, 23 May 2024 15:25:21 +0100,
Nina Schoetterl-Glausch <nsg@linux.ibm.com> wrote:
> 
> On Mon, 2020-11-02 at 16:40 +0000, Marc Zyngier wrote:

Wow, you're digging out the old dregs... But it is worth it!

>
> [...]
> 
> > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> > index dfb5218137ca..3f23f7478d2a 100644
> > --- a/arch/arm64/kvm/guest.c
> > +++ b/arch/arm64/kvm/guest.c
> > @@ -252,10 +252,32 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> >  	memcpy(addr, valp, KVM_REG_SIZE(reg->id));
> 
> I was looking at KVM_(G|S)ET_ONE_REG implementations and something looks off to me here:
> 
> ...
> 
> 	if (off == KVM_REG_ARM_CORE_REG(regs.pstate)) {
> 		u64 mode = (*(u64 *)valp) & PSR_AA32_MODE_MASK;
> 		switch (mode) {
> 
> Masking and switch over mode here...
> 
> 		case PSR_AA32_MODE_USR:
> 			if (!kvm_supports_32bit_el0())
> 				return -EINVAL;
> 			break;
> 		case PSR_AA32_MODE_FIQ:
> 		case PSR_AA32_MODE_IRQ:
> ...
> >  
> >  	if (*vcpu_cpsr(vcpu) & PSR_MODE32_BIT) {
> > -		int i;
> > +		int i, nr_reg;
> > +
> > +		switch (*vcpu_cpsr(vcpu)) {
> 
> ...but switching over mode without masking here.
> I don't know if this is as intended, but I thought I'd mention it.

Amazing. Thanks for spotting this. This is indeed broken. I guess this
was not spotted because userspace is not totally broken itself.

Do you want to submit a fix adding the masking back? or should I do it
myself?

Thanks again,

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2024-05-23 16:04 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-02 16:40 [PATCH v2 00/11] KVM: arm64: Move PC/ELR/SPSR/PSTATE updatess to EL2 Marc Zyngier
2020-11-02 16:40 ` Marc Zyngier
2020-11-02 16:40 ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 01/11] KVM: arm64: Don't adjust PC on SError during SMC trap Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 02/11] KVM: arm64: Move kvm_vcpu_trap_il_is32bit into kvm_skip_instr32() Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 03/11] KVM: arm64: Make kvm_skip_instr() and co private to HYP Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2021-05-05 14:23   ` Zenghui Yu
2021-05-05 14:23     ` Zenghui Yu
2021-05-05 14:23     ` Zenghui Yu
2021-05-05 16:46     ` Marc Zyngier
2021-05-05 16:46       ` Marc Zyngier
2021-05-05 16:46       ` Marc Zyngier
2021-05-06  6:33       ` Marc Zyngier
2021-05-06  6:33         ` Marc Zyngier
2021-05-06  6:33         ` Marc Zyngier
2021-05-06 11:43         ` Zenghui Yu
2021-05-06 11:43           ` Zenghui Yu
2021-05-06 11:43           ` Zenghui Yu
2021-05-06 14:29           ` Marc Zyngier
2021-05-06 14:29             ` Marc Zyngier
2021-05-06 14:29             ` Marc Zyngier
2021-05-09 13:07             ` Zenghui Yu
2021-05-09 13:07               ` Zenghui Yu
2021-05-09 13:07               ` Zenghui Yu
2021-05-10  7:59               ` Marc Zyngier
2021-05-10  7:59                 ` Marc Zyngier
2021-05-10  7:59                 ` Marc Zyngier
2021-05-06 17:17     ` Marc Zyngier
2021-05-06 17:17       ` Marc Zyngier
2021-05-06 17:17       ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 04/11] KVM: arm64: Move PC rollback on SError " Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 05/11] KVM: arm64: Move VHE direct sysreg accessors into kvm_host.h Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 06/11] KVM: arm64: Add basic hooks for injecting exceptions from EL2 Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 07/11] KVM: arm64: Inject AArch64 exceptions from HYP Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 08/11] KVM: arm64: Inject AArch32 " Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 09/11] KVM: arm64: Remove SPSR manipulation primitives Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 10/11] KVM: arm64: Consolidate exception injection Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40 ` [PATCH v2 11/11] KVM: arm64: Get rid of the AArch32 register mapping code Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2020-11-02 16:40   ` Marc Zyngier
2024-05-23 14:25   ` Nina Schoetterl-Glausch
2024-05-23 14:25     ` Nina Schoetterl-Glausch
2024-05-23 16:04     ` Marc Zyngier [this message]
2024-05-23 16:04       ` Marc Zyngier
2024-05-23 16:19       ` Nina Schoetterl-Glausch
2024-05-23 16:19         ` Nina Schoetterl-Glausch
2024-05-23 18:18         ` Marc Zyngier
2024-05-23 18:18           ` Marc Zyngier

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