Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757542Ab2BMSVD (ORCPT ); Mon, 13 Feb 2012 13:21:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:24795 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757456Ab2BMSVB (ORCPT ); Mon, 13 Feb 2012 13:21:01 -0500 From: Igor Mammedov To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, riel@redhat.com, amit.shah@redhat.com, mtosatti@redhat.com Subject: [PATCH] BUG in pv_clock when overflow condition is detected Date: Mon, 13 Feb 2012 19:20:56 +0100 Message-Id: <1329157256-19926-1-git-send-email-imammedo@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1229 Lines: 36 BUG when overflow occurs at pvclock.c:pvclock_get_nsec_offset u64 delta = native_read_tsc() - shadow->tsc_timestamp; this might happen at an attempt to read an uninitialized yet clock. It won't prevent stalls and hangs but at least it won't do it silently. Signed-off-by: Igor Mammedov --- arch/x86/kernel/pvclock.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index 42eb330..35a6190 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -43,7 +43,10 @@ void pvclock_set_flags(u8 flags) static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow) { - u64 delta = native_read_tsc() - shadow->tsc_timestamp; + u64 delta; + u64 tsc = native_read_tsc(); + BUG_ON(tsc < shadow->tsc_timestamp); + delta = tsc - shadow->tsc_timestamp; return pvclock_scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift); } -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/