From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754377AbcCGW5p (ORCPT ); Mon, 7 Mar 2016 17:57:45 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:39468 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753821AbcCGWyz (ORCPT ); Mon, 7 Mar 2016 17:54:55 -0500 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Simon Guinot , Linus Torvalds , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 189/273] kernel/resource.c: fix muxed resource handling in __request_region() Date: Mon, 7 Mar 2016 14:49:40 -0800 Message-Id: <1457391064-6660-190-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1457391064-6660-1-git-send-email-kamal@canonical.com> References: <1457391064-6660-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ 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: Kamal Mostafa --- kernel/resource.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/resource.c b/kernel/resource.c index fed052a..b8c8480 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -1072,9 +1072,10 @@ 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); -- 2.7.0