Will reports that with CONFIG_EXPERT=y and CONFIG_HARDEN_BRANCH_PREDICTOR=n, the kernel dereferences a NULL pointer during boot:

[ 2.384444] Internal error: Oops: 96000004 [#1] PREEMPT SMP [ 2.384461] pstate: 20400085 (nzCv daIf +PAN -UAO) [ 2.384472] pc : cpu_hyp_reinit+0x114/0x30c [ 2.384476] lr : cpu_hyp_reinit+0x80/0x30c

[ 2.384529] Call trace: [ 2.384533] cpu_hyp_reinit+0x114/0x30c [ 2.384537] _kvm_arch_hardware_enable+0x30/0x54 [ 2.384541] flush_smp_call_function_queue+0xe4/0x154 [ 2.384544] generic_smp_call_function_single_interrupt+0x10/0x18 [ 2.384549] ipi_handler+0x170/0x2b0 [ 2.384555] handle_percpu_devid_fasteoi_ipi+0x120/0x1cc [ 2.384560] __handle_domain_irq+0x9c/0xf4 [ 2.384563] gic_handle_irq+0x6c/0xe4 [ 2.384566] el1_irq+0xf0/0x1c0 [ 2.384570] arch_cpu_idle+0x28/0x44 [ 2.384574] do_idle+0x100/0x2a8 [ 2.384577] cpu_startup_entry+0x20/0x24 [ 2.384581] secondary_start_kernel+0x1b0/0x1cc [ 2.384589] Code: b9469d08 7100011f 540003ad 52800208 (f9400108) [ 2.384600] ---[ end trace 266d08dbf96ff143 ]--- [ 2.385171] Kernel panic - not syncing: Fatal exception in interrupt

In this configuration arm64_get_bp_hardening_data() returns NULL. Add a check in kvm_get_hyp_vector().

Cc: Will Deacon will@kernel.org Link: https://lore.kernel.org/linux-arm-kernel/20220408120041.GB27685@willie-the-t... Fixes: a68912a3ae3 ("KVM: arm64: Add templates for BHB mitigation sequences") Cc: stable@vger.kernel.org # 4.19 Signed-off-by: James Morse james.morse@arm.com --- arch/arm64/include/asm/kvm_mmu.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index 44d3fdbcdf62..0243b6d22453 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -439,7 +439,8 @@ static inline void *kvm_get_hyp_vector(void) int slot = -1;

if ((cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) || - cpus_have_const_cap(ARM64_SPECTRE_BHB)) && data->template_start) { + cpus_have_const_cap(ARM64_SPECTRE_BHB)) && + data && data->template_start) { vect = kern_hyp_va(kvm_ksym_ref(__bp_harden_hyp_vecs_start)); slot = data->hyp_vectors_slot; }