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[arp] Validate length of ARP packet 

There is no practical way to generate an underlength ARP packet since
an ARP packet is always padded up to the minimum Ethernet frame length
(or dropped by the receiving Ethernet hardware if incorrectly padded),
but the absence of an explicit check causes warnings from some
analysis tools.

Fix by adding an explicit check on the I/O buffer length.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2016-03-12 01:21:18 +00:00
parent 11396473f5
commit 64acfd9ddd
2 changed files with 17 additions and 0 deletions
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10
src/include/ipxe/if_arp.h
View File

@ -99,4 +99,14 @@ static inline void * arp_target_pa ( struct arphdr *arphdr ) {
return ( arp_target_ha ( arphdr ) + arphdr->ar_hln );
}
/** ARP packet length
*
* @v arphdr ARP header
* @ret len Length (including header)
*/
static inline size_t arp_len ( struct arphdr *arphdr ) {
return ( sizeof ( *arphdr ) +
( 2 * ( arphdr->ar_hln + arphdr->ar_pln ) ) );
}
#endif /* _IPXE_IF_ARP_H */

7
src/net/arp.c
View File

@ -139,8 +139,15 @@ static int arp_rx ( struct io_buffer *iobuf, struct net_device *netdev,
struct arp_net_protocol *arp_net_protocol;
struct net_protocol *net_protocol;
struct ll_protocol *ll_protocol;
size_t len = iob_len ( iobuf );
int rc;
/* Sanity check */
if ( ( len < sizeof ( *arphdr ) ) || ( len < arp_len ( arphdr ) ) ) {
rc = -EINVAL;
goto done;
}
/* Identify network-layer and link-layer protocols */
arp_net_protocol = arp_find_protocol ( arphdr->ar_pro );
if ( ! arp_net_protocol ) {