On 05/16/2013 02:29 PM, Alex Elder wrote:
Bjorn Helgaas pointed out that a recent commit introduced a
use-after-free condition in an error path for rbd_add().
He correctly stated:
I think b536f69a3a5 "rbd: set up devices only for mapped images"
introduced a use-after-free error in rbd_add():
...
If rbd_dev_device_setup() returns an error, we call
rbd_dev_image_release(), which ultimately kfrees rbd_dev.
Then we call rbd_dev_destroy(), which references fields in
the already-freed rbd_dev struct before kfreeing it again.
The simple fix is to return the error code after the call to
rbd_dev_image_release().
Closer examination revealed that there's no need to clean up
rbd_opts in that function, so fix that too.
Update some other comments that have also become out of date.
Reported-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
---
v2: call to ceph_destroy_options() moved to its own patch
drivers/block/rbd.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index ade30dd..fdbcf04 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -4700,8 +4700,10 @@ out:
return ret;
}
-/* Undo whatever state changes are made by v1 or v2 image probe */
-
+/*
+ * Undo whatever state changes are made by v1 or v2 header info
+ * call.
+ */
static void rbd_dev_unprobe(struct rbd_device *rbd_dev)
{
struct rbd_image_header *header;
@@ -4905,9 +4907,10 @@ static int rbd_dev_image_probe(struct rbd_device
*rbd_dev, bool mapping)
int tmp;
/*
- * Get the id from the image id object. If it's not a
- * format 2 image, we'll get ENOENT back, and we'll assume
- * it's a format 1 image.
+ * Get the id from the image id object. Unless there's an
+ * error, rbd_dev->spec->image_id will be filled in with
+ * a dynamically-allocated string, and rbd_dev->image_format
+ * will be set to either 1 or 2.
*/
ret = rbd_dev_image_id(rbd_dev);
if (ret)
@@ -5033,12 +5036,14 @@ static ssize_t rbd_add(struct bus_type *bus,
return count;
rbd_dev_image_release(rbd_dev);
It looks like rbd_dev_image_release() does all the needed cleanup
except the module_put(). Just adding a module_put() here would do the
trick I think, since rbd_dev_image_release() is also used for parent
images that don't call module_get() and module_put().
With that change:
Reviewed-by: Josh Durgin <josh.durgin@xxxxxxxxxxx>
+
+ return rc;
+
err_out_rbd_dev:
rbd_dev_destroy(rbd_dev);
err_out_client:
rbd_put_client(rbdc);
err_out_args:
- kfree(rbd_opts);
rbd_spec_put(spec);
err_out_module:
module_put(THIS_MODULE);
--
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