| From 2f9b68f57c6278c322793a06063181deded0ad69 Mon Sep 17 00:00:00 2001 |
| From: Vitaly Kuznetsov <vkuznets@redhat.com> |
| Date: Fri, 27 Aug 2021 11:25:14 +0200 |
| Subject: KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect() |
| |
| From: Vitaly Kuznetsov <vkuznets@redhat.com> |
| |
| commit 2f9b68f57c6278c322793a06063181deded0ad69 upstream. |
| |
| KASAN reports the following issue: |
| |
| BUG: KASAN: stack-out-of-bounds in kvm_make_vcpus_request_mask+0x174/0x440 [kvm] |
| Read of size 8 at addr ffffc9001364f638 by task qemu-kvm/4798 |
| |
| CPU: 0 PID: 4798 Comm: qemu-kvm Tainted: G X --------- --- |
| Hardware name: AMD Corporation DAYTONA_X/DAYTONA_X, BIOS RYM0081C 07/13/2020 |
| Call Trace: |
| dump_stack+0xa5/0xe6 |
| print_address_description.constprop.0+0x18/0x130 |
| ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] |
| __kasan_report.cold+0x7f/0x114 |
| ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] |
| kasan_report+0x38/0x50 |
| kasan_check_range+0xf5/0x1d0 |
| kvm_make_vcpus_request_mask+0x174/0x440 [kvm] |
| kvm_make_scan_ioapic_request_mask+0x84/0xc0 [kvm] |
| ? kvm_arch_exit+0x110/0x110 [kvm] |
| ? sched_clock+0x5/0x10 |
| ioapic_write_indirect+0x59f/0x9e0 [kvm] |
| ? static_obj+0xc0/0xc0 |
| ? __lock_acquired+0x1d2/0x8c0 |
| ? kvm_ioapic_eoi_inject_work+0x120/0x120 [kvm] |
| |
| The problem appears to be that 'vcpu_bitmap' is allocated as a single long |
| on stack and it should really be KVM_MAX_VCPUS long. We also seem to clear |
| the lower 16 bits of it with bitmap_zero() for no particular reason (my |
| guess would be that 'bitmap' and 'vcpu_bitmap' variables in |
| kvm_bitmap_or_dest_vcpus() caused the confusion: while the later is indeed |
| 16-bit long, the later should accommodate all possible vCPUs). |
| |
| Fixes: 7ee30bc132c6 ("KVM: x86: deliver KVM IOAPIC scan request to target vCPUs") |
| Fixes: 9a2ae9f6b6bb ("KVM: x86: Zero the IOAPIC scan request dest vCPUs bitmap") |
| Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com> |
| Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> |
| Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> |
| Reviewed-by: Sean Christopherson <seanjc@google.com> |
| Message-Id: <20210827092516.1027264-7-vkuznets@redhat.com> |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/kvm/ioapic.c | 10 +++++----- |
| 1 file changed, 5 insertions(+), 5 deletions(-) |
| |
| --- a/arch/x86/kvm/ioapic.c |
| +++ b/arch/x86/kvm/ioapic.c |
| @@ -319,8 +319,8 @@ static void ioapic_write_indirect(struct |
| unsigned index; |
| bool mask_before, mask_after; |
| union kvm_ioapic_redirect_entry *e; |
| - unsigned long vcpu_bitmap; |
| int old_remote_irr, old_delivery_status, old_dest_id, old_dest_mode; |
| + DECLARE_BITMAP(vcpu_bitmap, KVM_MAX_VCPUS); |
| |
| switch (ioapic->ioregsel) { |
| case IOAPIC_REG_VERSION: |
| @@ -384,9 +384,9 @@ static void ioapic_write_indirect(struct |
| irq.shorthand = APIC_DEST_NOSHORT; |
| irq.dest_id = e->fields.dest_id; |
| irq.msi_redir_hint = false; |
| - bitmap_zero(&vcpu_bitmap, 16); |
| + bitmap_zero(vcpu_bitmap, KVM_MAX_VCPUS); |
| kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq, |
| - &vcpu_bitmap); |
| + vcpu_bitmap); |
| if (old_dest_mode != e->fields.dest_mode || |
| old_dest_id != e->fields.dest_id) { |
| /* |
| @@ -399,10 +399,10 @@ static void ioapic_write_indirect(struct |
| kvm_lapic_irq_dest_mode( |
| !!e->fields.dest_mode); |
| kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq, |
| - &vcpu_bitmap); |
| + vcpu_bitmap); |
| } |
| kvm_make_scan_ioapic_request_mask(ioapic->kvm, |
| - &vcpu_bitmap); |
| + vcpu_bitmap); |
| } else { |
| kvm_make_scan_ioapic_request(ioapic->kvm); |
| } |