linux-kernel - [PATCH] ocfs2: Fix a use after free on error

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Date:   Mon, 1 Feb 2021 15:25:43 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Mark Fasheh <mark@...heh.com>, Jiri Slaby <jirislaby@...nel.org>
Cc:     Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Jens Axboe <axboe@...nel.dk>, ocfs2-devel@....oracle.com,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] ocfs2: Fix a use after free on error

The error handling in this function frees "reg" but it is still on the
"o2hb_all_regions" list so it will lead to a use after free.  The fix
for this is to only add it to the list after everything has succeeded.

Fixes: 1cf257f51191 ("ocfs2: fix memory leak")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
This is from static analysis and hasn't been tested.

 fs/ocfs2/cluster/heartbeat.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
index 0179a73a3fa2..92af4dc813e7 100644
--- a/fs/ocfs2/cluster/heartbeat.c
+++ b/fs/ocfs2/cluster/heartbeat.c
@@ -2025,7 +2025,6 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g
 		}
 		set_bit(reg->hr_region_num, o2hb_region_bitmap);
 	}
-	list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
 	spin_unlock(&o2hb_live_lock);
 
 	config_item_init_type_name(&reg->hr_item, name, &o2hb_region_type);
@@ -2053,6 +2052,10 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g
 
 	o2hb_debug_region_init(reg, o2hb_debug_dir);
 
+	spin_lock(&o2hb_live_lock);
+	list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
+	spin_unlock(&o2hb_live_lock);
+
 	return &reg->hr_item;
 
 unregister_handler:
-- 
2.29.2