Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756658AbcCBAJU (ORCPT ); Tue, 1 Mar 2016 19:09:20 -0500 Received: from mail177-1.suw61.mandrillapp.com ([198.2.177.1]:59827 "EHLO mail177-1.suw61.mandrillapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932559AbcCAX60 (ORCPT ); Tue, 1 Mar 2016 18:58:26 -0500 From: Greg Kroah-Hartman Subject: [PATCH 4.4 308/342] kernel/resource.c: fix muxed resource handling in __request_region() X-Mailer: git-send-email 2.7.2 To: Cc: Greg Kroah-Hartman , , Simon Guinot , Vincent Donnefort , Linus Torvalds Message-Id: <20160301234537.836314602@linuxfoundation.org> In-Reply-To: <20160301234527.990448862@linuxfoundation.org> References: <20160301234527.990448862@linuxfoundation.org> X-Report-Abuse: Please forward a copy of this message, including all headers, to abuse@mandrill.com X-Report-Abuse: You can also report abuse here: http://mandrillapp.com/contact/abuse?id=30481620.9334ba4c40e9491ea65259d4361638b2 X-Mandrill-User: md_30481620 Date: Tue, 01 Mar 2016 23:55:27 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1993 Lines: 52 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Simon Guinot commit 59ceeaaf355fa0fb16558ef7c24413c804932ada upstream. In __request_region, if a conflict with a BUSY and MUXED resource is detected, then the caller goes to sleep and waits for the resource to be released. A pointer on the conflicting resource is kept. At wake-up this pointer is used as a parent to retry to request the region. A first problem is that this pointer might well be invalid (if for example the conflicting resource have already been freed). Another problem is that the next call to __request_region() fails to detect a remaining conflict. The previously conflicting resource is passed as a parameter and __request_region() will look for a conflict among the children of this resource and not at the resource itself. It is likely to succeed anyway, even if there is still a conflict. Instead, the parent of the conflicting resource should be passed to __request_region(). As a fix, this patch doesn't update the parent resource pointer in the case we have to wait for a muxed region right after. Reported-and-tested-by: Vincent Pelletier Signed-off-by: Simon Guinot Tested-by: Vincent Donnefort Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/resource.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1083,9 +1083,10 @@ struct resource * __request_region(struc if (!conflict) break; if (conflict != parent) { - parent = conflict; - if (!(conflict->flags & IORESOURCE_BUSY)) + if (!(conflict->flags & IORESOURCE_BUSY)) { + parent = conflict; continue; + } } if (conflict->flags & flags & IORESOURCE_MUXED) { add_wait_queue(&muxed_resource_wait, &wait);