This is a note to let you know that I've just added the patch titled
ppp: reject claimed-as-LCP but actually malformed packets
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ppp-reject-claimed-as-lcp-but-actually-malformed-pac.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9d308da2bcf2c23807de4b6847b91c25b4348c66
Author: Dmitry Antipov <dmantipov@xxxxxxxxx>
Date: Mon Jul 8 14:56:15 2024 +0300
ppp: reject claimed-as-LCP but actually malformed packets
[ Upstream commit f2aeb7306a898e1cbd03963d376f4b6656ca2b55 ]
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 078c0f474f966..3cd4196b36b21 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -70,6 +70,7 @@
#define MPHDRLEN_SSN 4 /* ditto with short sequence numbers */
#define PPP_PROTO_LEN 2
+#define PPP_LCP_HDRLEN 4
/*
* An instance of /dev/ppp can be associated with either a ppp
@@ -491,6 +492,15 @@ 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)
+{
+ /* LCP packets must include LCP header which 4 bytes long:
+ * 1-byte code, 1-byte identifier, and 2-byte length.
+ */
+ return get_unaligned_be16(skb->data) != PPP_LCP ||
+ count >= PPP_PROTO_LEN + PPP_LCP_HDRLEN;
+}
+
static ssize_t ppp_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
@@ -513,6 +523,11 @@ 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:
