On Tue, Nov 5, 2024 at 12:45 AM Björn Töpel <bjorn@xxxxxxxxxx> wrote:
>
> From: Björn Töpel <bjorn@xxxxxxxxxxxx>
>
> In kvm_riscv_vcpu_sbi_init() the entry->ext_idx can contain an
> out-of-bound index. This is used as a special marker for the base
> extensions, that cannot be disabled. However, when traversing the
> extensions, that special marker is not checked prior indexing the
> array.
>
> Add an out-of-bounds check to the function.
>
> Fixes: 56d8a385b605 ("RISC-V: KVM: Allow some SBI extensions to be disabled by default")
> Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
> ---
> Don't know if it matters, but I hit this when trying kvmtool.
Looks like this went unnoticed. Thanks for catching.
Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
Queued this patch for Linux-6.13.
Thanks,
Anup
>
>
> Björn
> ---
> arch/riscv/kvm/vcpu_sbi.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index 7de128be8db9..6e704ed86a83 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -486,19 +486,22 @@ void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu)
> struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
> const struct kvm_riscv_sbi_extension_entry *entry;
> const struct kvm_vcpu_sbi_extension *ext;
> - int i;
> + int idx, i;
>
> for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
> entry = &sbi_ext[i];
> ext = entry->ext_ptr;
> + idx = entry->ext_idx;
> +
> + if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
> + continue;
>
> if (ext->probe && !ext->probe(vcpu)) {
> - scontext->ext_status[entry->ext_idx] =
> - KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
> + scontext->ext_status[idx] = KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
> continue;
> }
>
> - scontext->ext_status[entry->ext_idx] = ext->default_disabled ?
> + scontext->ext_status[idx] = ext->default_disabled ?
> KVM_RISCV_SBI_EXT_STATUS_DISABLED :
> KVM_RISCV_SBI_EXT_STATUS_ENABLED;
> }
>
> base-commit: 59b723cd2adbac2a34fc8e12c74ae26ae45bf230
> --
> 2.43.0
>
