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| author | Jens Axboe <jaxboe@fusionio.com> | 2011-06-05 06:01:13 +0200 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2011-06-06 05:57:21 +0200 |
| commit | 9b50902db5eb8a220160fb89e95aa11967998d12 (patch) | |
| tree | ad025360c616398f2b0aea1f0789a2f8174496b1 /block | |
| parent | 796d5116c407690b14fd5bda136aa67a39e7061a (diff) | |
| download | lwn-9b50902db5eb8a220160fb89e95aa11967998d12.tar.gz lwn-9b50902db5eb8a220160fb89e95aa11967998d12.zip | |
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@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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 a2fb14bb1402..000719c484c3 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2767,8 +2767,11 @@ 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]); |