From a6adb106225f9e2f177d3d883596e011df321965 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 22 Mar 2016 17:25:42 +0100 Subject: KVM: page_track: fix access to NULL slot This happens when doing the reboot test from virt-tests: [ 131.833653] BUG: unable to handle kernel NULL pointer dereference at (null) [ 131.842461] IP: [] kvm_page_track_is_active+0x17/0x60 [kvm] [ 131.850500] PGD 0 [ 131.852763] Oops: 0000 [#1] SMP [ 132.007188] task: ffff880075fbc500 ti: ffff880850a3c000 task.ti: ffff880850a3c000 [ 132.138891] Call Trace: [ 132.141639] [] page_fault_handle_page_track+0x31/0x40 [kvm] [ 132.149732] [] paging64_page_fault+0xff/0x910 [kvm] [ 132.172159] [] kvm_mmu_page_fault+0x64/0x110 [kvm] [ 132.179372] [] handle_exception+0x1b2/0x430 [kvm_intel] [ 132.187072] [] vmx_handle_exit+0x1e1/0xc50 [kvm_intel] ... Cc: Xiao Guangrong Fixes: 3d0c27ad6ee465f174b09ee99fcaf189c57d567a Signed-off-by: Paolo Bonzini --- arch/x86/kvm/page_track.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'arch') diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c index 11f76436f74f..b431539c3714 100644 --- a/arch/x86/kvm/page_track.c +++ b/arch/x86/kvm/page_track.c @@ -142,12 +142,17 @@ void kvm_slot_page_track_remove_page(struct kvm *kvm, bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn, enum kvm_page_track_mode mode) { - struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); - int index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL); + struct kvm_memory_slot *slot; + int index; if (WARN_ON(!page_track_mode_is_valid(mode))) return false; + slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); + if (!slot) + return false; + + index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL); return !!ACCESS_ONCE(slot->arch.gfn_track[mode][index]); } -- cgit v1.2.3