[PATCH 4.9 80/80] pstore: Shut down worker when unregistering

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@xxxxxxxxxxxx>

commit 6330d5534786d5315d56d558aa6d20740f97d80a upstream.

When built as a module and running with update_ms >= 0, pstore will Oops
during module unload since the work timer is still running. This makes sure
the worker is stopped before unloading.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/pstore/platform.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -704,6 +704,7 @@ int pstore_register(struct pstore_info *
 	if (psi->flags & PSTORE_FLAGS_PMSG)
 		pstore_register_pmsg();
 
+	/* Start watching for new records, if desired. */
 	if (pstore_update_ms >= 0) {
 		pstore_timer.expires = jiffies +
 			msecs_to_jiffies(pstore_update_ms);
@@ -726,6 +727,11 @@ EXPORT_SYMBOL_GPL(pstore_register);
 
 void pstore_unregister(struct pstore_info *psi)
 {
+	/* Stop timer and make sure all work has finished. */
+	pstore_update_ms = -1;
+	del_timer_sync(&pstore_timer);
+	flush_work(&pstore_work);
+
 	if (psi->flags & PSTORE_FLAGS_PMSG)
 		pstore_unregister_pmsg();
 	if (psi->flags & PSTORE_FLAGS_FTRACE)
@@ -825,7 +831,9 @@ static void pstore_timefunc(unsigned lon
 		schedule_work(&pstore_work);
 	}
 
-	mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
+	if (pstore_update_ms >= 0)
+		mod_timer(&pstore_timer,
+			  jiffies + msecs_to_jiffies(pstore_update_ms));
 }
 
 module_param(backend, charp, 0444);