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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: 3d0c27ad6e
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2016-03-22 17:25:42 +01:00
parent 0af574be32
commit a6adb10622
1 changed files with 7 additions and 2 deletions
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9
arch/x86/kvm/page_track.c
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@ -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, bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn,
enum kvm_page_track_mode mode) enum kvm_page_track_mode mode)
{ {
struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); struct kvm_memory_slot *slot;
int index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL); int index;
if (WARN_ON(!page_track_mode_is_valid(mode))) if (WARN_ON(!page_track_mode_is_valid(mode)))
return false; 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]); return !!ACCESS_ONCE(slot->arch.gfn_track[mode][index]);
} }