diff options
| author | Dmitry Antipov <dmantipov@yandex.ru> | 2024-07-08 14:56:15 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-07-18 11:39:37 +0200 |
| commit | 97d1efd8be26615ff680cdde86937d5943138f37 (patch) | |
| tree | 4ea1218680edd44c8faf0f9168ecf0c4b1d54991 | |
| parent | 1a2db00a554cfda57c397cce79b2804bf9633fec (diff) | |
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@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/net/ppp/ppp_generic.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 220b28711f98..5c737c6aa58b 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -74,6 +74,7 @@ #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 @@ -495,6 +496,15 @@ 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) { @@ -517,6 +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: |