diff options
authorMauro Carvalho Chehab <mchehab@s-opensource.com>2017-09-12 05:58:26 -0400
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2017-10-11 12:47:36 -0400
commitead666000a5fe34bdc82d61838e4df2d416ea15e (patch)
parentdb6321a1af8432df983048d2dd8529525589f71d (diff)
media: dvb_frontend: only use kref after initializedmedia/v4.14-2
As reported by Laurent, when a DVB frontend need to register two drivers (e. g. a tuner and a demod), if the second driver fails to register (for example because it was not compiled), the error handling logic frees the frontend by calling dvb_frontend_detach(). That used to work fine, but changeset 1f862a68df24 ("[media] dvb_frontend: move kref to struct dvb_frontend") added a kref at struct dvb_frontend. So, now, instead of just freeing the data, the error handling do a kref_put(). That works fine only after dvb_register_frontend() succeeds. While it would be possible to add a helper function that would be initializing earlier the kref, that would require changing every single DVB frontend on non-trivial ways, and would make frontends different than other drivers. So, instead of doing that, let's focus on the real issue: only call kref_put() after kref_init(). That's easy to check, as, when the dvb frontend is successfuly registered, it will allocate its own private struct. So, if such struct is allocated, it means that it is safe to use kref_put(). If not, then nobody is using yet the frontend, and it is safe to just deallocate it. Fixes: 1f862a68df24 ("[media] dvb_frontend: move kref to struct dvb_frontend") Reported-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
1 files changed, 21 insertions, 4 deletions
diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index 2fcba1616168..9139d01ba7ed 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -141,22 +141,39 @@ struct dvb_frontend_private {
static void dvb_frontend_invoke_release(struct dvb_frontend *fe,
void (*release)(struct dvb_frontend *fe));
-static void dvb_frontend_free(struct kref *ref)
+static void __dvb_frontend_free(struct dvb_frontend *fe)
- struct dvb_frontend *fe =
- container_of(ref, struct dvb_frontend, refcount);
struct dvb_frontend_private *fepriv = fe->frontend_priv;
+ if (!fepriv)
+ return;
dvb_frontend_invoke_release(fe, fe->ops.release);
+ fe->frontend_priv = NULL;
+static void dvb_frontend_free(struct kref *ref)
+ struct dvb_frontend *fe =
+ container_of(ref, struct dvb_frontend, refcount);
+ __dvb_frontend_free(fe);
static void dvb_frontend_put(struct dvb_frontend *fe)
- kref_put(&fe->refcount, dvb_frontend_free);
+ /*
+ * Check if the frontend was registered, as otherwise
+ * kref was not initialized yet.
+ */
+ if (fe->frontend_priv)
+ kref_put(&fe->refcount, dvb_frontend_free);
+ else
+ __dvb_frontend_free(fe);
static void dvb_frontend_get(struct dvb_frontend *fe)

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