From 2c10b61421a28e95a46ab489fd56c0f442ff6952 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Tue, 14 Feb 2023 11:33:04 +0100
Subject: [PATCH] kvm: initialize all of the kvm_debugregs structure before
 sending it to userspace
Git-commit: 2c10b61421a28e95a46ab489fd56c0f442ff6952
Patch-mainline: v6.2
References: bsc#1209532 CVE-2023-1513

When calling the KVM_GET_DEBUGREGS ioctl, on some configurations, there
might be some unitialized portions of the kvm_debugregs structure that
could be copied to userspace.  Prevent this as is done in the other kvm
ioctls, by setting the whole structure to 0 before copying anything into
it.

Bonus is that this reduces the lines of code as the explicit flag
setting and reserved space zeroing out can be removed.

Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: <x86@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: stable <stable@kernel.org>
Reported-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Message-id: <20230214103304.3689213-1-gregkh@linuxfoundation.org>
Tested-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Vasant Karasulli <vkarasulli@suse.de>

---
 arch/x86/kvm/x86.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f0fa3de2ceb8..a2c299d47e69 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5263,12 +5263,11 @@ static void kvm_vcpu_ioctl_x86_get_debugregs(struct kvm_vcpu *vcpu,
 {
 	unsigned long val;

+	memset(dbgregs, 0, sizeof(*dbgregs));
 	memcpy(dbgregs->db, vcpu->arch.db, sizeof(vcpu->arch.db));
 	kvm_get_dr(vcpu, 6, &val);
 	dbgregs->dr6 = val;
 	dbgregs->dr7 = vcpu->arch.dr7;
-	dbgregs->flags = 0;
-	memset(&dbgregs->reserved, 0, sizeof(dbgregs->reserved));
 }

 static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
--
2.34.1