net: validate variable length ll headers

Orabug: 25308053

[ Upstream commit 2793a23aacbd754dbbb5cb75093deb7e4103bace ]

Netdevice parameter hard_header_len is variously interpreted both as
an upper and lower bound on link layer header length. The field is
used as upper bound when reserving room at allocation, as lower bound
when validating user input in PF_PACKET.

Clarify the definition to be maximum header length. For validation
of untrusted headers, add an optional validate member to header_ops.

Allow bypassing of validation by passing CAP_SYS_RAWIO, for instance
for deliberate testing of corrupt input. In this case, pad trailing
bytes, as some device drivers expect completely initialized headers.

See also http://comments.gmane.org/gmane.linux.network/401064

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 1df16498dfd0d5a129bdf2982d9a08df73e8923d)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>
[dhaval.giani@oracle.com: Fixup KABI breakage in include/linux/netdevice.h]

Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f6e5cad155e75b19867fe5506ed689999bb4472c..d65d00c8fbdcff97510df9b556f8c98ec65125a5 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -265,6 +265,9 @@ struct header_ops {
        void    (*cache_update)(struct hh_cache *hh,
                                const struct net_device *dev,
                                const unsigned char *haddr);
+#ifndef __GENKSYMS__
+       bool    (*validate)(const char *ll_header, unsigned int len);
+#endif
 };
 
 /* These flag bits are private to the generic network queueing
@@ -1372,8 +1375,7 @@ enum netdev_priv_flags {
  *     @dma:           DMA channel
  *     @mtu:           Interface MTU value
  *     @type:          Interface hardware type
- *     @hard_header_len: Hardware header length, which means that this is the
- *                       minimum size of a packet.
+ *     @hard_header_len: Maximum hardware header length.
  *
  *     @needed_headroom: Extra headroom the hardware may need, but not in all
  *                       cases can this be guaranteed
@@ -2417,6 +2419,24 @@ static inline int dev_parse_header(const struct sk_buff *skb,
        return dev->header_ops->parse(skb, haddr);
 }
 
+/* ll_header must have at least hard_header_len allocated */
+static inline bool dev_validate_header(const struct net_device *dev,
+                                      char *ll_header, int len)
+{
+       if (likely(len >= dev->hard_header_len))
+               return true;
+
+       if (capable(CAP_SYS_RAWIO)) {
+               memset(ll_header + len, 0, dev->hard_header_len - len);
+               return true;
+       }
+
+       if (dev->header_ops && dev->header_ops->validate)
+               return dev->header_ops->validate(ll_header, len);
+
+       return false;
+}
+
 typedef int gifconf_func_t(struct net_device * dev, char __user * bufptr, int len);
 int register_gifconf(unsigned int family, gifconf_func_t *gifconf);
 static inline int unregister_gifconf(unsigned int family)