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authorPaolo Bonzini <pbonzini@redhat.com>2016-03-22 17:25:42 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2016-03-22 17:27:28 +0100
commita6adb106225f9e2f177d3d883596e011df321965 (patch)
treee2b8fe81450e9206be07492d7735d3ae276c9b2e /arch
parent0af574be32cddf8d0c2fbb194dcc635e73a83f1e (diff)
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: [<ffffffffa0950087>] 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] [<ffffffffa092bd11>] page_fault_handle_page_track+0x31/0x40 [kvm] [ 132.149732] [<ffffffffa093380f>] paging64_page_fault+0xff/0x910 [kvm] [ 132.172159] [<ffffffffa092c734>] kvm_mmu_page_fault+0x64/0x110 [kvm] [ 132.179372] [<ffffffffa06743c2>] handle_exception+0x1b2/0x430 [kvm_intel] [ 132.187072] [<ffffffffa067a301>] vmx_handle_exit+0x1e1/0xc50 [kvm_intel] ... Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com> Fixes: 3d0c27ad6ee465f174b09ee99fcaf189c57d567a Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/page_track.c9
1 files changed, 7 insertions, 2 deletions
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]);
}

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