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authorIlya Dryomov <idryomov@gmail.com>2015-10-11 19:38:00 +0200
committerIlya Dryomov <idryomov@gmail.com>2015-10-23 18:37:24 +0200
commit6d69bb536bac0d403d83db1ca841444981b280cd (patch)
tree1821420a26561ecad40a7d01b10d02a2993ce065
parent1f2c6651f69c14d0d3a9cfbda44ea101b02160ba (diff)
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rbd: prevent kernel stack blow up on rbd map
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>
-rw-r--r--drivers/block/rbd.c33
1 files changed, 23 insertions, 10 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 028db28cb8a0..6f26cf38c6f9 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -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;