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rbd: prevent kernel stack blow up on rbd map

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Mapping an image with a long parent chain (e.g. image foo, whose parent
is bar, whose parent is baz, etc) currently leads to a kernel stack
overflow, due to the following recursion in the reply path:

  rbd_osd_req_callback()
    rbd_obj_request_complete()
      rbd_img_obj_callback()
        rbd_img_parent_read_callback()
          rbd_obj_request_complete()
            ...

Limit the parent chain to 16 images, which is ~5K worth of stack.  When
the above recursion is eliminated, this limit can be lifted.

Fixes: http://tracker.ceph.com/issues/12538

Cc: stable@vger.kernel.org # 3.10+, needs backporting for < 4.2
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Josh Durgin <jdurgin@redhat.com>
This commit is contained in:
Ilya Dryomov 2015-10-11 19:38:00 +02:00
parent 1f2c6651f6
commit 6d69bb536b
1 changed files with 23 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
drivers/block/rbd.c
View File

@ -96,6 +96,8 @@ static int atomic_dec_return_safe(atomic_t *v)
#define RBD_MINORS_PER_MAJOR 256
#define RBD_SINGLE_MAJOR_PART_SHIFT 4
#define RBD_MAX_PARENT_CHAIN_LEN 16
#define RBD_SNAP_DEV_NAME_PREFIX "snap_"
#define RBD_MAX_SNAP_NAME_LEN \
(NAME_MAX - (sizeof (RBD_SNAP_DEV_NAME_PREFIX) - 1))
@ -426,7 +428,7 @@ static ssize_t rbd_add_single_major(struct bus_type *bus, const char *buf,
size_t count);
static ssize_t rbd_remove_single_major(struct bus_type *bus, const char *buf,
size_t count);
static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping);
static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth);
static void rbd_spec_put(struct rbd_spec *spec);
static int rbd_dev_id_to_minor(int dev_id)
@ -5131,7 +5133,12 @@ out_err:
return ret;
}
static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
/*
* @depth is rbd_dev_image_probe() -> rbd_dev_probe_parent() ->
* rbd_dev_image_probe() recursion depth, which means it's also the
* length of the already discovered part of the parent chain.
*/
static int rbd_dev_probe_parent(struct rbd_device *rbd_dev, int depth)
{
struct rbd_device *parent = NULL;
int ret;
@ -5139,6 +5146,12 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
if (!rbd_dev->parent_spec)
return 0;
if (++depth > RBD_MAX_PARENT_CHAIN_LEN) {
pr_info("parent chain is too long (%d)\n", depth);
ret = -EINVAL;
goto out_err;
}
parent = rbd_dev_create(rbd_dev->rbd_client, rbd_dev->parent_spec,
NULL);
if (!parent) {
@ -5153,7 +5166,7 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
__rbd_get_client(rbd_dev->rbd_client);
rbd_spec_get(rbd_dev->parent_spec);
ret = rbd_dev_image_probe(parent, false);
ret = rbd_dev_image_probe(parent, depth);
if (ret < 0)
goto out_err;
@ -5282,7 +5295,7 @@ static void rbd_dev_image_release(struct rbd_device *rbd_dev)
* parent), initiate a watch on its header object before using that
* object to get detailed information about the rbd image.
*/
static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
{
int ret;
@ -5300,7 +5313,7 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
if (ret)
goto err_out_format;
if (mapping) {
if (!depth) {
ret = rbd_dev_header_watch_sync(rbd_dev);
if (ret) {
if (ret == -ENOENT)
@ -5321,7 +5334,7 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
* Otherwise this is a parent image, identified by pool, image
* and snap ids - need to fill in names for those ids.
*/
if (mapping)
if (!depth)
ret = rbd_spec_fill_snap_id(rbd_dev);
else
ret = rbd_spec_fill_names(rbd_dev);
@ -5343,12 +5356,12 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
* Need to warn users if this image is the one being
* mapped and has a parent.
*/
if (mapping && rbd_dev->parent_spec)
if (!depth && rbd_dev->parent_spec)
rbd_warn(rbd_dev,
"WARNING: kernel layering is EXPERIMENTAL!");
}
ret = rbd_dev_probe_parent(rbd_dev);
ret = rbd_dev_probe_parent(rbd_dev, depth);
if (ret)
goto err_out_probe;
@ -5359,7 +5372,7 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping)
err_out_probe:
rbd_dev_unprobe(rbd_dev);
err_out_watch:
if (mapping)
if (!depth)
rbd_dev_header_unwatch_sync(rbd_dev);
out_header_name:
kfree(rbd_dev->header_name);
@ -5422,7 +5435,7 @@ static ssize_t do_rbd_add(struct bus_type *bus,
spec = NULL; /* rbd_dev now owns this */
rbd_opts = NULL; /* rbd_dev now owns this */
rc = rbd_dev_image_probe(rbd_dev, true);
rc = rbd_dev_image_probe(rbd_dev, 0);
if (rc < 0)
goto err_out_rbd_dev;