Implement a limit on on the number of IPv6 reassembly

queues per bucket.

There is a hashing algorithm which should distribute IPv6 reassembly
queues across the available buckets in a relatively even way. However,
if there is a flaw in the hashing algorithm which allows a large number
of IPv6 fragment reassembly queues to end up in a single bucket, a per-
bucket limit could help mitigate the performance impact of this flaw.

Implement such a limit, with a default of twice the maximum number of
reassembly queues divided by the number of buckets. Recalculate the
limit any time the maximum number of reassembly queues changes.
However, allow the user to override the value using a sysctl
(net.inet6.ip6.maxfragbucketsize).

Reviewed by:	jhb
Security:	FreeBSD-SA-18:10.ip
Security:	CVE-2018-6923
This commit is contained in:
jtl 2018-08-14 17:27:41 +00:00 committed by Sebastian Huber
parent 0e5c59050d
commit 823b096471
1 changed files with 2 additions and 1 deletions

View File

@ -643,7 +643,8 @@ struct ip6_mtuinfo {
#define IPV6CTL_INTRDQMAXLEN 52 /* max length of direct IPv6 netisr #define IPV6CTL_INTRDQMAXLEN 52 /* max length of direct IPv6 netisr
* queue */ * queue */
#define IPV6CTL_MAXFRAGSPERPACKET 53 /* Max fragments per packet */ #define IPV6CTL_MAXFRAGSPERPACKET 53 /* Max fragments per packet */
#define IPV6CTL_MAXID 54 #define IPV6CTL_MAXFRAGBUCKETSIZE 54 /* Max reassembly queues per bucket */
#define IPV6CTL_MAXID 55
#endif /* __BSD_VISIBLE */ #endif /* __BSD_VISIBLE */
/* /*