From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754321AbbLaQdm (ORCPT ); Thu, 31 Dec 2015 11:33:42 -0500 Received: from www.linutronix.de ([62.245.132.108]:46688 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750857AbbLaQbr (ORCPT ); Thu, 31 Dec 2015 11:31:47 -0500 Message-Id: <20151231160106.892412198@linutronix.de> User-Agent: quilt/0.63-1 Date: Thu, 31 Dec 2015 16:30:51 -0000 From: Thomas Gleixner To: LKML Cc: Ingo Molnar , Peter Anvin , Jiang Liu , Joe Lawrence , Jeremiah Mahler , Borislav Petkov , andy.shevchenko@gmail.com, Guenter Roeck Subject: [patch 10/14] x86/irq: Clear move_in_progress before sending cleanup IPI References: <20151231155849.772553760@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=x86-irq--Protect-send_cleanup_vector-with-vector_lock.patch X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org send_cleanup_vector() fiddles with the old_domain mask unprotected because it relies on the protection by the move_in_progress flag. But this is fatal, as the flag is reset after the IPI has been sent. So a cpu which receives the IPI can still see the flag set and therefor ignores the cleanup request. If no other cleanup request happens then the vector stays stale on that cpu and in case of an irq removal the vector still persists. That can lead to use after free when the next cleanup IPI happens. Protect the code with vector_lock and clear move_in_progress before sending the IPI. This does not plug the race which Joe reported because: CPU0 CPU1 CPU2 lock_vector() data->move_in_progress=0 sendIPI() unlock_vector() set_affinity() assign_irq_vector() lock_vector() handle_IPI move_in_progress = 1 lock_vector() unlock_vector() move_in_progress == 1 The full fix comes with a later patch. Reported-by: Joe Lawrence Signed-off-by: Thomas Gleixner --- arch/x86/kernel/apic/vector.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/apic/vector.c +++ b/arch/x86/kernel/apic/vector.c @@ -530,6 +530,8 @@ static void __send_cleanup_vector(struct { cpumask_var_t cleanup_mask; + raw_spin_lock(&vector_lock); + data->move_in_progress = 0; if (unlikely(!alloc_cpumask_var(&cleanup_mask, GFP_ATOMIC))) { unsigned int i; @@ -541,7 +543,7 @@ static void __send_cleanup_vector(struct apic->send_IPI_mask(cleanup_mask, IRQ_MOVE_CLEANUP_VECTOR); free_cpumask_var(cleanup_mask); } - data->move_in_progress = 0; + raw_spin_unlock(&vector_lock); } void send_cleanup_vector(struct irq_cfg *cfg)