[BACKPORT PATCH 5.10.y] KVM: arm64: Fix buffer overflow in kvm_arm_set_fw_reg()

[Will Deacon <will@kernel.org>]

From: Dan Carpenter <dan.carpenter@linaro.org>

[ Upstream commit a25bc8486f9c01c1af6b6c5657234b2eee2c39d6 ]

The KVM_REG_SIZE() comes from the ioctl and it can be a power of two
between 0-32768 but if it is more than sizeof(long) this will corrupt
memory.

Fixes: 99adb567632b ("KVM: arm/arm64: Add save/restore support for firmware workaround state")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/4efbab8c-640f-43b2-8ac6-6d68e08280fe@kili.mountain
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Cc: stable@vger.kernel.org # 5.10 and 5.15
[will: kvm_arm_set_fw_reg() lives in psci.c not hypercalls.c]
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kvm/psci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 20ba5136ac3d..32bb26be8a9b 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -499,6 +499,8 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	u64 val;
 	int wa_level;
 
+	if (KVM_REG_SIZE(reg->id) != sizeof(val))
+		return -ENOENT;
 	if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
 		return -EFAULT;
 
-- 
2.40.0.634.g4ca3ef3211-goog