From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: netdev@vger.kernel.org
Cc: davem@davemloft.net, Willem de Bruijn <willemb@google.com>,
Eric Dumazet <edumazet@google.com>
Subject: [PATCH net 1/2] tun: read vnet_hdr_sz once
Date: Fri, 3 Feb 2017 18:20:48 -0500 [thread overview]
Message-ID: <20170203232049.38982-2-willemdebruijn.kernel@gmail.com> (raw)
In-Reply-To: <20170203232049.38982-1-willemdebruijn.kernel@gmail.com>
From: Willem de Bruijn <willemb@google.com>
When IFF_VNET_HDR is enabled, a virtio_net header must precede data.
Data length is verified to be greater than or equal to expected header
length tun->vnet_hdr_sz before copying.
Read this value once and cache locally, as it can be updated between
the test and use (TOCTOU).
Signed-off-by: Willem de Bruijn <willemb@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
CC: Eric Dumazet <edumazet@google.com>
---
drivers/net/tun.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2cd10b26b650..bfabe180053e 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1170,9 +1170,11 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
}
if (tun->flags & IFF_VNET_HDR) {
- if (len < tun->vnet_hdr_sz)
+ int vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
+
+ if (len < vnet_hdr_sz)
return -EINVAL;
- len -= tun->vnet_hdr_sz;
+ len -= vnet_hdr_sz;
if (!copy_from_iter_full(&gso, sizeof(gso), from))
return -EFAULT;
@@ -1183,7 +1185,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
if (tun16_to_cpu(tun, gso.hdr_len) > len)
return -EINVAL;
- iov_iter_advance(from, tun->vnet_hdr_sz - sizeof(gso));
+ iov_iter_advance(from, vnet_hdr_sz - sizeof(gso));
}
if ((tun->flags & TUN_TYPE_MASK) == IFF_TAP) {
@@ -1335,7 +1337,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
vlan_hlen = VLAN_HLEN;
if (tun->flags & IFF_VNET_HDR)
- vnet_hdr_sz = tun->vnet_hdr_sz;
+ vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
total = skb->len + vlan_hlen + vnet_hdr_sz;
--
2.11.0.483.g087da7b7c-goog
next prev parent reply other threads:[~2017-02-03 23:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-03 23:20 [PATCH net 0/2] read vnet_hdr_sz once Willem de Bruijn
2017-02-03 23:20 ` Willem de Bruijn [this message]
2017-02-03 23:27 ` [PATCH net 1/2] tun: " Eric Dumazet
2017-02-03 23:20 ` [PATCH net 2/2] macvtap: read vnet_hdr_size once Willem de Bruijn
2017-02-03 23:27 ` Eric Dumazet
2017-02-07 3:48 ` [PATCH net 0/2] read vnet_hdr_sz once David Miller
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