On 06/25/2014 12:16 PM, Ilya Dryomov wrote:
> Linger requests that have not yet been registered should not be
> unregistered by __unregister_linger_request(). This messes up ref
> count and leads to use-after-free.
This makes sense. The problem can occur when updating the OSD
map. An OSD *client* has its list of linger requests, but they
are not all necessarily registered as associated with the *OSD*.
So the __unregister_linger_request() call in kick_requests()
might pass a not-yet-registered linger request.
It could also occur if a client (like RBD) gets an error after
setting a request to linger but the request has completed
successfully.
Anyway, looks good. This explains why the rename of the
r_linger_osd_item field was helpful.
Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
>
> Signed-off-by: Ilya Dryomov <ilya.dryomov@xxxxxxxxxxx>
> ---
> net/ceph/osd_client.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index a9b7ea7bfdc6..12ec553a7e76 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -1248,7 +1248,9 @@ static void __cancel_request(struct ceph_osd_request *req)
> static void __register_linger_request(struct ceph_osd_client *osdc,
> struct ceph_osd_request *req)
> {
> - dout("__register_linger_request %p\n", req);
> + dout("%s %p tid %llu\n", __func__, req, req->r_tid);
> + WARN_ON(!req->r_linger);
> +
> ceph_osdc_get_request(req);
> list_add_tail(&req->r_linger_item, &osdc->req_linger);
> if (req->r_osd)
> @@ -1259,8 +1261,17 @@ static void __register_linger_request(struct ceph_osd_client *osdc,
> static void __unregister_linger_request(struct ceph_osd_client *osdc,
> struct ceph_osd_request *req)
> {
> - dout("__unregister_linger_request %p\n", req);
> + WARN_ON(!req->r_linger);
> +
> + if (list_empty(&req->r_linger_item)) {
> + dout("%s %p tid %llu not registered\n", __func__, req,
> + req->r_tid);
> + return;
> + }
> +
> + dout("%s %p tid %llu\n", __func__, req, req->r_tid);
> list_del_init(&req->r_linger_item);
> +
> if (req->r_osd) {
> list_del_init(&req->r_linger_osd_item);
> maybe_move_osd_to_lru(osdc, req->r_osd);
>
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