[PATCH 3.10 78/80] kernel/resource.c: fix muxed resource handling in __request_region()

Path	csiph.com!news.freedyn.net!aioe.org!gothmog.csi.it!bofh.it!news.nic.it!robomod
From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 3.10 78/80] kernel/resource.c: fix muxed resource handling in __request_region()
Date	Wed, 02 Mar 2016 03:20:02 +0100
Message-ID	<r84ym-144-9@gated-at.bofh.it> (permalink)
References	<r82dd-7Iy-17@gated-at.bofh.it>
X-Mailer	git-send-email 2.7.2
User-Agent	quilt/0.64
MIME-Version	1.0
Content-Type	text/plain; charset=UTF-8
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	52
Organization	linux.* mail to news gateway
X-Original-Cc	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, stable@vger.kernel.org, Simon Guinot <simon.guinot@sequanux.org>, Vincent Donnefort <vdonnefort@gmail.com>, Linus Torvalds <torvalds@linux-foundation.org>
X-Original-Date	Tue, 1 Mar 2016 15:46:12 -0800
X-Original-Message-ID	<20160301234352.121431236@linuxfoundation.org>
X-Original-References	<20160301234349.667990420@linuxfoundation.org>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1347635

Show key headers only | View raw

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Simon Guinot <simon.guinot@sequanux.org>

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 <plr.vincent@gmail.com>
Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Tested-by: Vincent Donnefort <vdonnefort@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/resource.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -961,9 +961,10 @@ 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);

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH 3.10 78/80] kernel/resource.c: fix muxed resource handling in __request_region() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-03-02 03:20 +0100

csiph-web