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From:   Paolo Bonzini <pbonzini@redhat.com>
To:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@intel.com>
Subject: [PATCH] KVM: x86: fix access code passed to gva_to_gpa
Date:   Mon, 17 Aug 2020 14:00:42 -0400
Message-Id: <20200817180042.32264-1-pbonzini@redhat.com>
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The PK bit of the error code is computed dynamically in permission_fault
and therefore need not be passed to gva_to_gpa: only the access bits
(fetch, user, write) need to be passed down.

Not doing so causes a splat in the pku test:

   WARNING: CPU: 25 PID: 5465 at arch/x86/kvm/mmu.h:197 paging64_walk_addr_generic+0x594/0x750 [kvm]
   Hardware name: Intel Corporation WilsonCity/WilsonCity, BIOS WLYDCRB1.SYS.0014.D62.2001092233 01/09/2020
   RIP: 0010:paging64_walk_addr_generic+0x594/0x750 [kvm]
   Code: <0f> 0b e9 db fe ff ff 44 8b 43 04 4c 89 6c 24 30 8b 13 41 39 d0 89
   RSP: 0018:ff53778fc623fb60 EFLAGS: 00010202
   RAX: 0000000000000001 RBX: ff53778fc623fbf0 RCX: 0000000000000007
   RDX: 0000000000000001 RSI: 0000000000000002 RDI: ff4501efba818000
   RBP: 0000000000000020 R08: 0000000000000005 R09: 00000000004000e7
   R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000007
   R13: ff4501efba818388 R14: 10000000004000e7 R15: 0000000000000000
   FS:  00007f2dcf31a700(0000) GS:ff4501f1c8040000(0000) knlGS:0000000000000000
   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
   CR2: 0000000000000000 CR3: 0000001dea475005 CR4: 0000000000763ee0
   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
   DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
   PKRU: 55555554
   Call Trace:
    paging64_gva_to_gpa+0x3f/0xb0 [kvm]
    kvm_fixup_and_inject_pf_error+0x48/0xa0 [kvm]
    handle_exception_nmi+0x4fc/0x5b0 [kvm_intel]
    kvm_arch_vcpu_ioctl_run+0x911/0x1c10 [kvm]
    kvm_vcpu_ioctl+0x23e/0x5d0 [kvm]
    ksys_ioctl+0x92/0xb0
    __x64_sys_ioctl+0x16/0x20
    do_syscall_64+0x3e/0xb0
    entry_SYSCALL_64_after_hwframe+0x44/0xa9
   ---[ end trace d17eb998aee991da ]---

Reported-by: Sean Christopherson <sean.j.christopherson@intel.com>
Fixes: 897861479c064 ("KVM: x86: Add helper functions for illegal GPA checking and page fault injection")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/x86.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2db369a64f29..a6e42ce607ca 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10743,9 +10743,13 @@ EXPORT_SYMBOL_GPL(kvm_spec_ctrl_test_value);
 void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code)
 {
 	struct x86_exception fault;
+	const unsigned access_mask =
+		PFERR_WRITE_MASK | PFERR_FETCH_MASK | PFERR_USER_MASK;
 
 	if (!(error_code & PFERR_PRESENT_MASK) ||
-	    vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva, error_code, &fault) != UNMAPPED_GVA) {
+	    vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva,
+					    error_code & access_mask,
+					    &fault) != UNMAPPED_GVA) {
 		/*
 		 * If vcpu->arch.walk_mmu->gva_to_gpa succeeded, the page
 		 * tables probably do not match the TLB.  Just proceed
-- 
2.26.2