netdev - [PATCH 18/29] l2tp: WARN_ON rather than BUG_ON in l2tp

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Date:   Tue, 21 Jul 2020 18:32:10 +0100
From:   Tom Parkin <tparkin@...alix.com>
To:     netdev@...r.kernel.org
Cc:     Tom Parkin <tparkin@...alix.com>
Subject: [PATCH 18/29] l2tp: WARN_ON rather than BUG_ON in l2tp_debugfs.c

l2tp_dfs_seq_start had a BUG_ON to catch a possible programming error in
l2tp_dfs_seq_open.

Since we can easily bail out of l2tp_dfs_seq_start, prefer to do that
and flag the error with a WARN_ON rather than crashing the kernel.

Signed-off-by: Tom Parkin <tparkin@...alix.com>
---
 net/l2tp/l2tp_debugfs.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c
index 117a6697da72..800a17b988be 100644
--- a/net/l2tp/l2tp_debugfs.c
+++ b/net/l2tp/l2tp_debugfs.c
@@ -72,7 +72,14 @@ static void *l2tp_dfs_seq_start(struct seq_file *m, loff_t *offs)
 	if (!pos)
 		goto out;
 
-	BUG_ON(!m->private);
+	/* Unexpected: m->private is set in l2tp_dfs_seq_open.
+	 * Warn on this and bail out early.
+	 */
+	if (!m->private) {
+		WARN_ON(!m->private);
+		pd = NULL;
+		goto out;
+	}
 	pd = m->private;
 
 	if (!pd->tunnel)
-- 
2.17.1