remoteproc: Fix unbalanced boot with sysfs for no auto-boot rprocs

The remoteproc core performs automatic boot and shutdown of a remote
processor during rproc_add() and rproc_del() for remote processors
supporting 'auto-boot'. The remoteproc devices not using 'auto-boot'
require either a remoteproc client driver or a userspace client to
use the sysfs 'state' variable to perform the boot and shutdown. The
in-kernel client drivers hold the corresponding remoteproc driver
module's reference count when they acquire a rproc handle through
the rproc_get_by_phandle() API, but there is no such support for
userspace applications performing the boot through sysfs interface.

The shutdown of a remoteproc upon removing a remoteproc platform
driver is automatic only with 'auto-boot' and this can cause a
remoteproc with no auto-boot to stay powered on and never freed
up if booted using the sysfs interface without a matching stop,
and when the remoteproc driver module is removed or unbound from
the device. This will result in a memory leak as well as the
corresponding remoteproc ida being never deallocated. Fix this
by holding a module reference count for the remoteproc's driver
during a sysfs 'start' and releasing it during the sysfs 'stop'
operation.

Signed-off-by: Suman Anna <s-anna@ti.com>

diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
index 184c899b7a0d163283fce3158ce061c4aab92400..6b7e8b2b43be0753ba55296d1ada1b5525c53fc8 100644 (file)
--- a/drivers/remoteproc/remoteproc_sysfs.c
+++ b/drivers/remoteproc/remoteproc_sysfs.c
@@ -11,6 +11,7 @@
  * GNU General Public License for more details.
  */
 
+#include <linux/module.h>
 #include <linux/remoteproc.h>
 
 #include "remoteproc_internal.h"
@@ -84,14 +85,27 @@ static ssize_t state_store(struct device *dev,
                if (rproc->state == RPROC_RUNNING)
                        return -EBUSY;
 
+               /*
+                * prevent underlying implementation from being removed
+                * when remoteproc does not support auto-boot
+                */
+               if (!rproc->auto_boot &&
+                   !try_module_get(dev->parent->driver->owner))
+                       return -EINVAL;
+
                ret = rproc_boot(rproc);
-               if (ret)
+               if (ret) {
                        dev_err(&rproc->dev, "Boot failed: %d\n", ret);
+                       if (!rproc->auto_boot)
+                               module_put(dev->parent->driver->owner);
+               }
        } else if (sysfs_streq(buf, "stop")) {
                if (rproc->state != RPROC_RUNNING)
                        return -EINVAL;
 
                rproc_shutdown(rproc);
+               if (!rproc->auto_boot)
+                       module_put(dev->parent->driver->owner);
        } else {
                dev_err(&rproc->dev, "Unrecognised option: %s\n", buf);
                ret = -EINVAL;