linux-kernel - [PATCH 28/91] cfq-iosched: fix locking around ioc->ioc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20120205220950.642723239@pcw.home.local>
Date:	Sun, 05 Feb 2012 23:10:17 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Jens Axboe <jaxboe@...ionio.com>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: [PATCH 28/91] cfq-iosched: fix locking around ioc->ioc_data assignment

2.6.27-longterm review patch.  If anyone has any objections, please let us know.

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

commit ab4bd22d3cce6977dc039664cc2d052e3147d662 upstream.

Since we are modifying this RCU pointer, we need to hold
the lock protecting it around it.

This fixes a potential reuse and double free of a cfq
io_context structure. The bug has been in CFQ for a long
time, it hit very few people but those it did hit seemed
to see it a lot.

Tracked in RH bugzilla here:

https://bugzilla.redhat.com/show_bug.cgi?id=577968

Credit goes to Paul Bolle for figuring out that the issue
was around the one-hit ioc->ioc_data cache. Thanks to his
hard work the issue is now fixed.

Signed-off-by: Jens Axboe <jaxboe@...ionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 block/cfq-iosched.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

Index: longterm-2.6.27/block/cfq-iosched.c
===================================================================
--- longterm-2.6.27.orig/block/cfq-iosched.c	2012-02-05 22:34:34.185915429 +0100
+++ longterm-2.6.27/block/cfq-iosched.c	2012-02-05 22:34:38.850917663 +0100
@@ -1286,8 +1286,11 @@
 	cic->dead_key = (unsigned long) cic->key;
 	cic->key = NULL;
 
-	if (ioc->ioc_data == cic)
+	if (rcu_dereference(ioc->ioc_data) == cic) {
+		spin_lock(&ioc->lock);
 		rcu_assign_pointer(ioc->ioc_data, NULL);
+		spin_unlock(&ioc->lock);
+	}
 
 	if (cic->cfqq[ASYNC]) {
 		cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/