diff options
| author | Jens Axboe <jaxboe@fusionio.com> | 2011-06-05 06:01:13 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-07-13 05:29:24 +0200 |
| commit | 1ff36a0e02f978e533b13ce6a86ad6a73444cec8 (patch) | |
| tree | f51ea39985a7b77710aae2552a4df1204c10a90e /block | |
| parent | 336fca97910371e16506e5448ad0ca9daae9a59c (diff) | |
cfq-iosched: fix locking around ioc->ioc_data assignment
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@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'block')
| -rw-r--r-- | block/cfq-iosched.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index aa1e9535e35..da7327edaa1 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1540,8 +1540,11 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd, 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[BLK_RW_ASYNC]) { cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]); |