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rbd: fix use-after free of rbd_dev->disk

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Removing a device deallocates the disk, unschedules the watch, and
finally cleans up the rbd_dev structure. rbd_dev_refresh(), called
from the watch callback, updates the disk size and rbd_dev
structure. With no locking between them, rbd_dev_refresh() may use the
device or rbd_dev after they've been freed.

To fix this, check whether RBD_DEV_FLAG_REMOVING is set before
updating the disk size in rbd_dev_refresh(). In order to prevent a
race where rbd_dev_refresh() is already revalidating the disk when
rbd_remove() is called, move the call to rbd_bus_del_dev() after the
watch is unregistered and all notifies are complete. It's safe to
defer deleting this structure because no new requests can be submitted
once the RBD_DEV_FLAG_REMOVING is set, since the device cannot be
opened.

Fixes: http://tracker.ceph.com/issues/5636
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
This commit is contained in:
Josh Durgin 2013-08-29 17:26:31 -07:00
parent 20e0af67ce
commit 9875201e10
1 changed files with 33 additions and 7 deletions
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40
drivers/block/rbd.c
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@ -3325,6 +3325,31 @@ static void rbd_exists_validate(struct rbd_device *rbd_dev)
clear_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
}
static void rbd_dev_update_size(struct rbd_device *rbd_dev)
{
sector_t size;
bool removing;
/*
* Don't hold the lock while doing disk operations,
* or lock ordering will conflict with the bdev mutex via:
* rbd_add() -> blkdev_get() -> rbd_open()
*/
spin_lock_irq(&rbd_dev->lock);
removing = test_bit(RBD_DEV_FLAG_REMOVING, &rbd_dev->flags);
spin_unlock_irq(&rbd_dev->lock);
/*
* If the device is being removed, rbd_dev->disk has
* been destroyed, so don't try to update its size
*/
if (!removing) {
size = (sector_t)rbd_dev->mapping.size / SECTOR_SIZE;
dout("setting size to %llu sectors", (unsigned long long)size);
set_capacity(rbd_dev->disk, size);
revalidate_disk(rbd_dev->disk);
}
}
static int rbd_dev_refresh(struct rbd_device *rbd_dev)
{
u64 mapping_size;
@ -3344,12 +3369,7 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev)
up_write(&rbd_dev->header_rwsem);
if (mapping_size != rbd_dev->mapping.size) {
sector_t size;
size = (sector_t)rbd_dev->mapping.size / SECTOR_SIZE;
dout("setting size to %llu sectors", (unsigned long long)size);
set_capacity(rbd_dev->disk, size);
revalidate_disk(rbd_dev->disk);
rbd_dev_update_size(rbd_dev);
}
return ret;
@ -5160,7 +5180,6 @@ static ssize_t rbd_remove(struct bus_type *bus,
if (ret < 0 || already)
return ret;
rbd_bus_del_dev(rbd_dev);
ret = rbd_dev_header_watch_sync(rbd_dev, false);
if (ret)
rbd_warn(rbd_dev, "failed to cancel watch event (%d)\n", ret);
@ -5171,6 +5190,13 @@ static ssize_t rbd_remove(struct bus_type *bus,
*/
dout("%s: flushing notifies", __func__);
ceph_osdc_flush_notifies(&rbd_dev->rbd_client->client->osdc);
/*
* Don't free anything from rbd_dev->disk until after all
* notifies are completely processed. Otherwise
* rbd_bus_del_dev() will race with rbd_watch_cb(), resulting
* in a potential use after free of rbd_dev->disk or rbd_dev.
*/
rbd_bus_del_dev(rbd_dev);
rbd_dev_image_release(rbd_dev);
module_put(THIS_MODULE);