diff options
| author | Willem de Bruijn <willemb@google.com> | 2017-02-03 18:20:48 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-02-06 22:41:27 -0500 |
| commit | e1edab87faf6ca30cd137e0795bc73aa9a9a22ec (patch) | |
| tree | 6bed425132b0eb1c3808a012ad5f81799df0d78c | |
| parent | ccf7abb93af09ad0868ae9033d1ca8108bdaec82 (diff) | |
| download | linux-e1edab87faf6ca30cd137e0795bc73aa9a9a22ec.tar.bz2 | |
tun: read vnet_hdr_sz once
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>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | drivers/net/tun.c | 10 |
1 files 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; |