netdev - [PATCH 6/9] l2tp: don't BUG_ON seqfile checks in l2tp

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 24 Jul 2020 16:31:54 +0100
From:   Tom Parkin <tparkin@...alix.com>
To:     netdev@...r.kernel.org
Cc:     jchapman@...alix.com, Tom Parkin <tparkin@...alix.com>
Subject: [PATCH 6/9] l2tp: don't BUG_ON seqfile checks in l2tp_ppp

checkpatch advises that WARN_ON and recovery code are preferred over
BUG_ON which crashes the kernel.

l2tp_ppp has a BUG_ON check of struct seq_file's private pointer in
pppol2tp_seq_start prior to accessing data through that pointer.

Rather than crashing, we can simply bail out early and return NULL in
order to terminate the seq file processing in much the same way as we do
when reaching the end of tunnel/session instances to render.

Retain a WARN_ON to help trace possible bugs in this area.

Signed-off-by: Tom Parkin <tparkin@...alix.com>
---
 net/l2tp/l2tp_ppp.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 3b6613cfef48..c2d14cecbecf 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -1478,7 +1478,11 @@ static void *pppol2tp_seq_start(struct seq_file *m, loff_t *offs)
 	if (!pos)
 		goto out;

-	BUG_ON(!m->private);
+	if (WARN_ON(!m->private)) {
+		pd = NULL;
+		goto out;
+	}
+
 	pd = m->private;
 	net = seq_file_net(m);

-- 
2.17.1