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authorWillem de Bruijn <willemb@google.com>2017-02-03 18:20:48 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-18 16:39:27 +0100
commit625bd9e43b3b6a5d796c6a5bac660dc405a60fa2 (patch)
tree6ecb8b8717326a83d670ccfd71f94aab42de451d /drivers/net
parent82e9f6b90a0e7fbc017bdce23845c7580db6f657 (diff)
downloadlinux-linaro-stable-625bd9e43b3b6a5d796c6a5bac660dc405a60fa2.tar.gz
tun: read vnet_hdr_sz once
[ Upstream commit e1edab87faf6ca30cd137e0795bc73aa9a9a22ec ] 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/net')
-rw-r--r--drivers/net/tun.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 111b972e3053..c31d8e74f131 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1108,9 +1108,11 @@ 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;
n = copy_from_iter(&gso, sizeof(gso), from);
if (n != sizeof(gso))
@@ -1122,7 +1124,7 @@ 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) {
@@ -1301,7 +1303,7 @@ 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;