[PATCH 4.19 302/338] KVM: arm64: Check arm64_get_bp_hardening_data() didnt return NULL

Greg Kroah-Hartman
2022-04-14T14:00:22Z

From: James Morse <james.morse@arm.com>

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-truck/
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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;
}
--
2.35.1