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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Andy Price <anprice@redhat.com>,
        Bob Peterson <rpeterso@redhat.com>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 019/221] gfs2: fix use-after-free in trans_drain
Date:   Mon, 29 Mar 2021 09:55:50 +0200
Message-Id: <20210329075629.827560716@linuxfoundation.org>
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From: Bob Peterson <rpeterso@redhat.com>

[ Upstream commit 1a5a2cfd34c17db73c53ef127272c8c1ae220485 ]

This patch adds code to function trans_drain to remove drained
bd elements from the ail lists, if queued, before freeing the bd.
If we don't remove the bd from the ail, function ail_drain will
try to reference the bd after it has been freed by trans_drain.

Thanks to Andy Price for his analysis of the problem.

Reported-by: Andy Price <anprice@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/gfs2/log.c   | 4 ++++
 fs/gfs2/trans.c | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 2e9314091c81..1955dea999f7 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -935,12 +935,16 @@ static void trans_drain(struct gfs2_trans *tr)
 	while (!list_empty(head)) {
 		bd = list_first_entry(head, struct gfs2_bufdata, bd_list);
 		list_del_init(&bd->bd_list);
+		if (!list_empty(&bd->bd_ail_st_list))
+			gfs2_remove_from_ail(bd);
 		kmem_cache_free(gfs2_bufdata_cachep, bd);
 	}
 	head = &tr->tr_databuf;
 	while (!list_empty(head)) {
 		bd = list_first_entry(head, struct gfs2_bufdata, bd_list);
 		list_del_init(&bd->bd_list);
+		if (!list_empty(&bd->bd_ail_st_list))
+			gfs2_remove_from_ail(bd);
 		kmem_cache_free(gfs2_bufdata_cachep, bd);
 	}
 }
diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c
index 6d4bf7ea7b3b..7f850ff6a05d 100644
--- a/fs/gfs2/trans.c
+++ b/fs/gfs2/trans.c
@@ -134,6 +134,8 @@ static struct gfs2_bufdata *gfs2_alloc_bufdata(struct gfs2_glock *gl,
 	bd->bd_bh = bh;
 	bd->bd_gl = gl;
 	INIT_LIST_HEAD(&bd->bd_list);
+	INIT_LIST_HEAD(&bd->bd_ail_st_list);
+	INIT_LIST_HEAD(&bd->bd_ail_gl_list);
 	bh->b_private = bd;
 	return bd;
 }
-- 
2.30.1