KVM: arm64: Fix buffer overflow in kvm_arm_set_fw_reg()

commit a25bc8486f9c01c1af6b6c5657234b2eee2c39d6 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index c9f401f..950e35b 100644 (file)
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -397,6 +397,8 @@ 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;