[PATCH 13/15] staging: gasket: core: protect against races during unregister

[Todd Poynor <toddpoynor@gmail.com>]

From: Todd Poynor <toddpoynor@google.com>

Keep mutex held across the unregistration operation, until the
driver_desc field of the global table is removed, to prevent a
concurrent accessor from looking up the driver_desc while
gasket_unregister_device() is in the processing of removing it.

Reported-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
---
 drivers/staging/gasket/gasket_core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/staging/gasket/gasket_core.c b/drivers/staging/gasket/gasket_core.c
index ace92f107ed58..a6462b6d702f1 100644
--- a/drivers/staging/gasket/gasket_core.c
+++ b/drivers/staging/gasket/gasket_core.c
@@ -1765,9 +1765,9 @@ void gasket_unregister_device(const struct gasket_driver_desc *driver_desc)
 			break;
 		}
 	}
-	mutex_unlock(&g_mutex);
 
 	if (!internal_desc) {
+		mutex_unlock(&g_mutex);
 		pr_err("request to unregister unknown desc: %s, %d:%d\n",
 		       driver_desc->name, driver_desc->major,
 		       driver_desc->minor);
@@ -1780,7 +1780,6 @@ void gasket_unregister_device(const struct gasket_driver_desc *driver_desc)
 	class_destroy(internal_desc->class);
 
 	/* Finally, effectively "remove" the driver. */
-	mutex_lock(&g_mutex);
 	g_descs[desc_idx].driver_desc = NULL;
 	mutex_unlock(&g_mutex);
 
-- 
2.18.0.597.ga71716f1ad-goog