This is a note to let you know that I've just added the patch titled
arm: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: arm-kvm-fix-smccc-handling-of-unimplemented-smc-hvc-calls.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 20e8175d246e9f9deb377f2784b3e7dfb2ad3e86 Mon Sep 17 00:00:00 2001
From: Marc Zyngier marc.zyngier@arm.com Date: Tue, 6 Feb 2018 17:56:06 +0000 Subject: arm: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls
From: Marc Zyngier marc.zyngier@arm.com
commit 20e8175d246e9f9deb377f2784b3e7dfb2ad3e86 upstream.
KVM doesn't follow the SMCCC when it comes to unimplemented calls, and inject an UNDEF instead of returning an error. Since firmware calls are now used for security mitigation, they are becoming more common, and the undef is counter productive.
Instead, let's follow the SMCCC which states that -1 must be returned to the caller when getting an unknown function number.
Tested-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm/kvm/handle_exit.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
--- a/arch/arm/kvm/handle_exit.c +++ b/arch/arm/kvm/handle_exit.c @@ -45,7 +45,7 @@ static int handle_hvc(struct kvm_vcpu *v
ret = kvm_psci_call(vcpu); if (ret < 0) { - kvm_inject_undefined(vcpu); + vcpu_set_reg(vcpu, 0, ~0UL); return 1; }
@@ -54,7 +54,16 @@ static int handle_hvc(struct kvm_vcpu *v
static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run) { - kvm_inject_undefined(vcpu); + /* + * "If an SMC instruction executed at Non-secure EL1 is + * trapped to EL2 because HCR_EL2.TSC is 1, the exception is a + * Trap exception, not a Secure Monitor Call exception [...]" + * + * We need to advance the PC after the trap, as it would + * otherwise return to the same address... + */ + vcpu_set_reg(vcpu, 0, ~0UL); + kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu)); return 1; }
Patches currently in stable-queue which might be from marc.zyngier@arm.com are
queue-4.4/arm-kvm-fix-smccc-handling-of-unimplemented-smc-hvc-calls.patch