[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <20240705160808.113296-1-dmantipov@yandex.ru>
Date: Fri, 5 Jul 2024 19:08:08 +0300
From: Dmitry Antipov <dmantipov@...dex.ru>
To: "David S . Miller" <davem@...emloft.net>
Cc: linux-ppp@...r.kernel.org,
netdev@...r.kernel.org,
lvc-project@...uxtesting.org,
Dmitry Antipov <dmantipov@...dex.ru>,
syzbot+ec0723ba9605678b14bf@...kaller.appspotmail.com
Subject: [PATCH] net: ppp: reject claimed-as-LCP but actually malformed packets
Since 'ppp_async_encode()' assumes valid LCP packets (with code
from 1 to 7 inclusive), add 'ppp_check_packet()' to ensure that
LCP packet has an actual body beyond PPP_LCP header bytes, and
reject claimed-as-LCP but actually malformed data otherwise.
Reported-by: syzbot+ec0723ba9605678b14bf@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf
Signed-off-by: Dmitry Antipov <dmantipov@...dex.ru>
---
drivers/net/ppp/ppp_generic.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 0a65b6d690fe..2c8dfeb8ca58 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -493,6 +493,18 @@ static ssize_t ppp_read(struct file *file, char __user *buf,
return ret;
}
+static bool ppp_check_packet(struct sk_buff *skb, size_t count)
+{
+ if (get_unaligned_be16(skb->data) == PPP_LCP &&
+ count < PPP_PROTO_LEN + 4)
+ /* Claimed as LCP but has no actual LCP body,
+ * which is 4 bytes at least (code, identifier,
+ * and 2-byte length).
+ */
+ return false;
+ return true;
+}
+
static ssize_t ppp_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
@@ -515,6 +527,11 @@ static ssize_t ppp_write(struct file *file, const char __user *buf,
kfree_skb(skb);
goto out;
}
+ ret = -EINVAL;
+ if (unlikely(!ppp_check_packet(skb, count))) {
+ kfree_skb(skb);
+ goto out;
+ }
switch (pf->kind) {
case INTERFACE:
--
2.45.2
Powered by blists - more mailing lists