linux-kernel - [PATCH 4.14 108/143] kvm: x86: fix WARN due to uninitialized guest FPU state

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Message-Id: <20181102182906.466254364@linuxfoundation.org>
Date:   Fri,  2 Nov 2018 19:34:53 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Xu <peterx@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 108/143] kvm: x86: fix WARN due to uninitialized guest FPU state

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

commit 5663d8f9bbe4bf15488f7351efb61ea20fa6de06 upstream

------------[ cut here ]------------
 Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers.
 WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90
 CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G    B      OE    4.15.0-rc2+ #10
 RIP: 0010:ex_handler_fprestore+0x88/0x90
 Call Trace:
  fixup_exception+0x4e/0x60
  do_general_protection+0xff/0x270
  general_protection+0x22/0x30
 RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm]
 RSP: 0018:ffff8803d5627810 EFLAGS: 00010246
  kvm_vcpu_reset+0x3b4/0x3c0 [kvm]
  kvm_apic_accept_events+0x1c0/0x240 [kvm]
  kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm]
  kvm_vcpu_ioctl+0x479/0x880 [kvm]
  do_vfs_ioctl+0x142/0x9a0
  SyS_ioctl+0x74/0x80
  do_syscall_64+0x15f/0x600

where kvm_put_guest_fpu is called without a prior kvm_load_guest_fpu.
To fix it, move kvm_load_guest_fpu to the very beginning of
kvm_arch_vcpu_ioctl_run.

Cc: stable@...r.kernel.org
Fixes: f775b13eedee2f7f3c6fdd4e90fb79090ce5d339
Signed-off-by: Peter Xu <peterx@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
Acked-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/x86.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3856828ee1dc..8d688b213504 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7393,13 +7393,12 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
 
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
-	struct fpu *fpu = &current->thread.fpu;
 	int r;
 
-	fpu__initialize(fpu);
-
 	kvm_sigset_activate(vcpu);
 
+	kvm_load_guest_fpu(vcpu);
+
 	if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
 		if (kvm_run->immediate_exit) {
 			r = -EINTR;
@@ -7440,6 +7439,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		r = vcpu_run(vcpu);
 
 out:
+	kvm_put_guest_fpu(vcpu);
 	post_kvm_run_save(vcpu);
 	kvm_sigset_deactivate(vcpu);
 
-- 
2.17.1