Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759344AbcCDJIL (ORCPT ); Fri, 4 Mar 2016 04:08:11 -0500 Received: from mx2.suse.de ([195.135.220.15]:59762 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759133AbcCDJDz (ORCPT ); Fri, 4 Mar 2016 04:03:55 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Simon Guinot , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 111/116] kernel/resource.c: fix muxed resource handling in __request_region() Date: Fri, 4 Mar 2016 10:02:36 +0100 Message-Id: <2976c211bd096c472f996a368030eb1c18cb174c.1457082108.git.jslaby@suse.cz> X-Mailer: git-send-email 2.7.2 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2085 Lines: 55 From: Simon Guinot 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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: Jiri Slaby --- kernel/resource.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/resource.c b/kernel/resource.c index 3f285dce9347..449282e48bb1 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -961,9 +961,10 @@ struct resource * __request_region(struct resource *parent, 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); -- 2.7.2