From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 12 Nov 2021 07:53:41 +0000 (-0500)
Subject: KVM: x86: move guest_pv_has out of user_access section
X-Git-Tag: v5.16-rc1~29^2~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3e067fd8503d6205aa0c1c8f48f6b209c592d19c;p=thirdparty%2Fkernel%2Flinux.git

KVM: x86: move guest_pv_has out of user_access section

When UBSAN is enabled, the code emitted for the call to guest_pv_has
includes a call to __ubsan_handle_load_invalid_value.  objtool
complains that this call happens with UACCESS enabled; to avoid
the warning, pull the calls to user_access_begin into both arms
of the "if" statement, after the check for guest_pv_has.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dd7b8b4656754..dc7eb5fddfd3e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3292,9 +3292,6 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 	}
 
 	st = (struct kvm_steal_time __user *)ghc->hva;
-	if (!user_access_begin(st, sizeof(*st)))
-		return;
-
 	/*
 	 * Doing a TLB flush here, on the guest's behalf, can avoid
 	 * expensive IPIs.
@@ -3303,6 +3300,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 		u8 st_preempted = 0;
 		int err = -EFAULT;
 
+		if (!user_access_begin(st, sizeof(*st)))
+			return;
+
 		asm volatile("1: xchgb %0, %2\n"
 			     "xor %1, %1\n"
 			     "2:\n"
@@ -3325,6 +3325,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 		if (!user_access_begin(st, sizeof(*st)))
 			goto dirty;
 	} else {
+		if (!user_access_begin(st, sizeof(*st)))
+			return;
+
 		unsafe_put_user(0, &st->preempted, out);
 		vcpu->arch.st.preempted = 0;
 	}