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tun: read vnet_hdr_sz once

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commit e1edab87faf6ca30cd137e0795bc73aa9a9a22ec upstream.

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).

[js] we have TUN_VNET_HDR in 3.12

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: Jiri Slaby <jslaby@suse.cz>
[wt: s/READ_ONCE/ACCESS_ONCE]
Signed-off-by: Willy Tarreau <w@1wt.eu>
This commit is contained in:
Willem de Bruijn
2017-02-03 18:20:48 -05:00
committed by Willy Tarreau
parent 58e4633a08
commit 302c74b132
1 changed files with 6 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/net/tun.c
+6 -4
View File
@@ -1087,9 +1087,11 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
}
if (tun->flags & TUN_VNET_HDR) {
if (len < tun->vnet_hdr_sz)
int vnet_hdr_sz = ACCESS_ONCE(tun->vnet_hdr_sz);
if (len < vnet_hdr_sz)
return -EINVAL;
len -= tun->vnet_hdr_sz;
len -= vnet_hdr_sz;
if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso)))
return -EFAULT;
@@ -1100,7 +1102,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
if (gso.hdr_len > len)
return -EINVAL;
offset += tun->vnet_hdr_sz;
offset += vnet_hdr_sz;
}
if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
@@ -1275,7 +1277,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
int vnet_hdr_sz = 0;
if (tun->flags & TUN_VNET_HDR)
vnet_hdr_sz = tun->vnet_hdr_sz;
vnet_hdr_sz = ACCESS_ONCE(tun->vnet_hdr_sz);
if (!(tun->flags & TUN_NO_PI)) {
if ((len -= sizeof(pi)) < 0)