lkml.org 
[lkml]   [2022]   [May]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.10 004/163] KVM: x86/mmu: fix NULL pointer dereference on guest INVPCID
Date
From: Paolo Bonzini <pbonzini@redhat.com>

commit 9f46c187e2e680ecd9de7983e4d081c3391acc76 upstream.

With shadow paging enabled, the INVPCID instruction results in a call
to kvm_mmu_invpcid_gva. If INVPCID is executed with CR0.PG=0, the
invlpg callback is not set and the result is a NULL pointer dereference.
Fix it trivially by checking for mmu->invlpg before every call.

There are other possibilities:

- check for CR0.PG, because KVM (like all Intel processors after P5)
flushes guest TLB on CR0.PG changes so that INVPCID/INVLPG are a
nop with paging disabled

- check for EFER.LMA, because KVM syncs and flushes when switching
MMU contexts outside of 64-bit mode

All of these are tricky, go for the simple solution. This is CVE-2022-1789.

Reported-by: Yongkang Jia <kangel@zju.edu.cn>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[fix conflict due to missing b9e5603c2a3accbadfec570ac501a54431a6bdba]
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/mmu/mmu.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5178,14 +5178,16 @@ void kvm_mmu_invpcid_gva(struct kvm_vcpu
uint i;

if (pcid == kvm_get_active_pcid(vcpu)) {
- mmu->invlpg(vcpu, gva, mmu->root_hpa);
+ if (mmu->invlpg)
+ mmu->invlpg(vcpu, gva, mmu->root_hpa);
tlb_flush = true;
}

for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
if (VALID_PAGE(mmu->prev_roots[i].hpa) &&
pcid == kvm_get_pcid(vcpu, mmu->prev_roots[i].pgd)) {
- mmu->invlpg(vcpu, gva, mmu->prev_roots[i].hpa);
+ if (mmu->invlpg)
+ mmu->invlpg(vcpu, gva, mmu->prev_roots[i].hpa);
tlb_flush = true;
}
}

\
 
 \ /
  Last update: 2022-05-27 11:03    [W:0.930 / U:0.176 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site