stm class: Fix unbalanced module/device refcounting
STM code takes references to the stm device and its module for the
duration of the character device's existence or the stm_source link.
Dropping these references is not well balanced everywhere, which may
lead to leaks.
This patch balances the acquisition and releasing of these two
references and annotates each site so that it's easier to verify
correctness by reading the code.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index f6ade21..f86f56d 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -113,6 +113,7 @@
stm = to_stm_device(dev);
if (!try_module_get(stm->owner)) {
+ /* matches class_find_device() above */
put_device(dev);
return NULL;
}
@@ -125,7 +126,7 @@
* @stm: stm device, previously acquired by stm_find_device()
*
* This drops the module reference and device reference taken by
- * stm_find_device().
+ * stm_find_device() or stm_char_open().
*/
void stm_put_device(struct stm_device *stm)
{
@@ -365,6 +366,8 @@
return nonseekable_open(inode, file);
err_free:
+ /* matches class_find_device() above */
+ put_device(dev);
kfree(stmf);
return err;
@@ -375,6 +378,11 @@
struct stm_file *stmf = file->private_data;
stm_output_free(stmf->stm, &stmf->output);
+
+ /*
+ * matches the stm_char_open()'s
+ * class_find_device() + try_module_get()
+ */
stm_put_device(stmf->stm);
kfree(stmf);
@@ -539,10 +547,8 @@
ret = stm->data->link(stm->data, stmf->output.master,
stmf->output.channel);
- if (ret) {
+ if (ret)
stm_output_free(stmf->stm, &stmf->output);
- stm_put_device(stmf->stm);
- }
err_free:
kfree(id);
@@ -679,6 +685,7 @@
return 0;
err_device:
+ /* matches device_initialize() above */
put_device(&stm->dev);
err_free:
kfree(stm);
@@ -791,7 +798,6 @@
fail_free_output:
stm_output_free(stm, &src->output);
- stm_put_device(stm);
fail_detach:
mutex_lock(&stm->link_mutex);
@@ -905,8 +911,10 @@
return -EINVAL;
err = stm_source_link_add(src, link);
- if (err)
+ if (err) {
+ /* matches the stm_find_device() above */
stm_put_device(link);
+ }
return err ? : count;
}