staging: bcm2835-audio: Fix memory corruption

The previous commit (0adbfd46) fixed a memory leak but also freed a
block in the success case, causing a stale pointer to be used with
potentially fatal results. Only free the vchi_instance block in the
case that vchi_connect fails; once connected, the instance is
retained for subsequent connections.

Simplifying the code by removing a bunch of gotos and returning errors
directly.

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
Fixes: 0adbfd4694c2 ("staging: bcm2835-audio: fix memory leak in bcm2835_audio_open_connection()")
Cc: stable <stable@vger.kernel.org> # 4.12+
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c
index 5f3d8f2..4be864d 100644 (file)
--- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c
+++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c
@@ -390,8 +390,7 @@ static int bcm2835_audio_open_connection(struct bcm2835_alsa_stream *alsa_stream
                        __func__, instance);
                instance->alsa_stream = alsa_stream;
                alsa_stream->instance = instance;
-               ret = 0; // xxx todo -1;
-               goto err_free_mem;
+               return 0;
        }
 
        /* Initialize and create a VCHI connection */
@@ -401,16 +400,15 @@ static int bcm2835_audio_open_connection(struct bcm2835_alsa_stream *alsa_stream
                        LOG_ERR("%s: failed to initialise VCHI instance (ret=%d)\n",
                                __func__, ret);
 
-                       ret = -EIO;
-                       goto err_free_mem;
+                       return -EIO;
                }
                ret = vchi_connect(NULL, 0, vchi_instance);
                if (ret) {
                        LOG_ERR("%s: failed to connect VCHI instance (ret=%d)\n",
                                __func__, ret);
 
-                       ret = -EIO;
-                       goto err_free_mem;
+                       kfree(vchi_instance);
+                       return -EIO;
                }
                initted = 1;
        }
@@ -421,19 +419,16 @@ static int bcm2835_audio_open_connection(struct bcm2835_alsa_stream *alsa_stream
        if (IS_ERR(instance)) {
                LOG_ERR("%s: failed to initialize audio service\n", __func__);
 
-               ret = PTR_ERR(instance);
-               goto err_free_mem;
+               /* vchi_instance is retained for use the next time. */
+               return PTR_ERR(instance);
        }
 
        instance->alsa_stream = alsa_stream;
        alsa_stream->instance = instance;
 
        LOG_DBG(" success !\n");
-       ret = 0;
-err_free_mem:
-       kfree(vchi_instance);
 
-       return ret;
+       return 0;
 }
 
 int bcm2835_audio_open(struct bcm2835_alsa_stream *alsa_stream)