[kernel/f15] Fix oopses in the CFQ disk scheduler (rhbz#577968)

[Chuck Ebbert]

commit d111c750cc6b38f8ad7d52520d97f742f4c58a3a
Author: Chuck Ebbert <cebbert at redhat.com>
Date:   Fri Jun 24 17:02:32 2011 -0400

    Fix oopses in the CFQ disk scheduler (rhbz#577968)

 ...ix-locking-around-ioc-ioc-data-assignment.patch |   44 ++++++++++++++++++++
 kernel.spec                                        |    4 ++
 2 files changed, 48 insertions(+), 0 deletions(-)
---
diff --git a/cfq-iosched-fix-locking-around-ioc-ioc-data-assignment.patch b/cfq-iosched-fix-locking-around-ioc-ioc-data-assignment.patch
new file mode 100644
index 0000000..bb04d63
--- /dev/null
+++ b/cfq-iosched-fix-locking-around-ioc-ioc-data-assignment.patch
@@ -0,0 +1,44 @@
+From: Jens Axboe <jaxboe at fusionio.com>
+Date: Sun, 5 Jun 2011 04:01:13 +0000 (+0200)
+Subject: cfq-iosched: fix locking around ioc->ioc_data assignment
+X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=ab4bd22d3cce6977dc039664cc2d052e3147d662
+
+cfq-iosched: fix locking around ioc->ioc_data assignment
+
+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.
+
+Cc: stable at kernel.org
+Signed-off-by: Jens Axboe <jaxboe at fusionio.com>
+---
+
+diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
+index 3c7b537..545b8d4 100644
+--- a/block/cfq-iosched.c
++++ b/block/cfq-iosched.c
+@@ -2772,8 +2772,11 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
+ 	smp_wmb();
+ 	cic->key = cfqd_dead_key(cfqd);
+ 
+-	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[BLK_RW_ASYNC]) {
+ 		cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
diff --git a/kernel.spec b/kernel.spec
index 80ee3ca..0339b76 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -665,6 +665,7 @@ Patch580: linux-2.6-sparc-selinux-mprotect-checks.patch
 Patch600: block-queue-refcount.patch
 Patch601: block-export-blk_-get-put-_queue.patch
 Patch602: block-blkdev_get-should-access-bd_disk-only-after.patch
+Patch603: cfq-iosched-fix-locking-around-ioc-ioc-data-assignment.patch
 
 # libata
 Patch620: ahci-add-another-pci-id-for-marvell.patch
@@ -1298,6 +1299,8 @@ ApplyPatch x86-pci-preserve-existing-pci-bfsort-whitelist-for-dell-systems.patch
 ApplyPatch block-queue-refcount.patch
 ApplyPatch block-export-blk_-get-put-_queue.patch
 ApplyPatch block-blkdev_get-should-access-bd_disk-only-after.patch
+# rhbz#577968
+ApplyPatch cfq-iosched-fix-locking-around-ioc-ioc-data-assignment.patch
 
 # libata
 ApplyPatch ahci-add-another-pci-id-for-marvell.patch
@@ -2053,6 +2056,7 @@ fi
 - CVE-2011-2183: ksm: race between ksmd and exiting task
 - Revert 2.6.38.8 patch that broke magicmouse (rhbz#714381)
 - Fix drive detection failure on mvsas (rhbz#705019)
+- Fix oopses in the CFQ disk scheduler (rhbz#577968)
 
 * Thu Jun 23 2011 Dave Airlie <airlied at redhat.com> 2.6.38.8-34
 - drm-i915-snb-irq-stalls-fix.patch: fix Sandybridge IRQ stalls