Re: [PATCH] KVM: page_track: fix access to NULL slot

2016-03-22 Thread Xiao Guangrong 



On 03/23/2016 12:40 AM, Paolo Bonzini wrote:

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:  [#1] SMP
[  132.007188] task: 880075fbc500 ti: 880850a3c000 task.ti: 
880850a3c000
[  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]
...


Thank you for fixing it, Paolo!

Reviewed-by: Xiao Guangrong

Re: [PATCH] KVM: page_track: fix access to NULL slot

2016-03-22 Thread Xiao Guangrong 



On 03/23/2016 12:40 AM, Paolo Bonzini wrote:

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:  [#1] SMP
[  132.007188] task: 880075fbc500 ti: 880850a3c000 task.ti: 
880850a3c000
[  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]
...


Thank you for fixing it, Paolo!

Reviewed-by: Xiao Guangrong

[PATCH] KVM: page_track: fix access to NULL slot

2016-03-22 Thread Paolo Bonzini 
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:  [#1] SMP
[  132.007188] task: 880075fbc500 ti: 880850a3c000 task.ti: 
880850a3c000
[  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(-)

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]);
 }
 
-- 
1.8.3.1

[PATCH] KVM: page_track: fix access to NULL slot

2016-03-22 Thread Paolo Bonzini 
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:  [#1] SMP
[  132.007188] task: 880075fbc500 ti: 880850a3c000 task.ti: 
880850a3c000
[  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(-)

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]);
 }
 
-- 
1.8.3.1