linux-kernel - [PATCH 4.19 85/97] staging: greybus: use after free in gb_audio_manager_remove

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Message-Id: <20200227132228.491814386@linuxfoundation.org>
Date:   Thu, 27 Feb 2020 14:37:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vaibhav Agarwal <vaibhav.sr@...il.com>
Subject: [PATCH 4.19 85/97] staging: greybus: use after free in gb_audio_manager_remove_all()

From: Dan Carpenter <dan.carpenter@...cle.com>

commit b7db58105b80fa9232719c8329b995b3addfab55 upstream.

When we call kobject_put() and it's the last reference to the kobject
then it calls gb_audio_module_release() and frees module.  We dereference
"module" on the next line which is a use after free.

Fixes: c77f85bbc91a ("greybus: audio: Fix incorrect counting of 'ida'")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
Reviewed-by: Vaibhav Agarwal <vaibhav.sr@...il.com>
Link: https://lore.kernel.org/r/20200205123217.jreendkyxulqsool@kili.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/greybus/audio_manager.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/greybus/audio_manager.c
+++ b/drivers/staging/greybus/audio_manager.c
@@ -89,8 +89,8 @@ void gb_audio_manager_remove_all(void)
 
 	list_for_each_entry_safe(module, next, &modules_list, list) {
 		list_del(&module->list);
-		kobject_put(&module->kobj);
 		ida_simple_remove(&module_id, module->id);
+		kobject_put(&module->kobj);
 	}
 
 	is_empty = list_empty(&modules_list);