Author: kp
Date: Mon Aug 20 14:27:37 2018
New Revision: 338104
URL: https://svnweb.freebsd.org/changeset/base/338104
Log:
MFC r337969:
pf: Limit the maximum number of fragments per packet
Similar to the network stack issue fixed in r337782 pf did not limit the
number
of fragments per packet, which could be exploited to generate high CPU loads
with a crafted series of packets.
Limit each packet to no more than 64 fragments. This should be sufficient on
typical networks to allow maximum-sized IP frames.
This addresses the issue for both IPv4 and IPv6.
Security: CVE-2018-5391
Sponsored by: Klara Systems
Modified:
stable/11/sys/netpfil/pf/pf_norm.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/netpfil/pf/pf_norm.c
==============================================================================
--- stable/11/sys/netpfil/pf/pf_norm.c Mon Aug 20 13:42:22 2018
(r338103)
+++ stable/11/sys/netpfil/pf/pf_norm.c Mon Aug 20 14:27:37 2018
(r338104)
@@ -90,8 +90,10 @@ struct pf_fragment {
TAILQ_ENTRY(pf_fragment) frag_next;
uint32_t fr_timeout;
uint16_t fr_maxlen; /* maximum length of single fragment */
+ uint16_t fr_entries; /* Total number of pf_fragment entries
*/
TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
};
+#define PF_MAX_FRENT_PER_FRAGMENT 64
struct pf_fragment_tag {
uint16_t ft_hdrlen; /* header length of reassembled pkt */
@@ -376,6 +378,7 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct
*(struct pf_fragment_cmp *)frag = *key;
frag->fr_timeout = time_uptime;
frag->fr_maxlen = frent->fe_len;
+ frag->fr_entries = 0;
TAILQ_INIT(&frag->fr_queue);
RB_INSERT(pf_frag_tree, &V_pf_frag_tree, frag);
@@ -387,6 +390,9 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct
return (frag);
}
+ if (frag->fr_entries >= PF_MAX_FRENT_PER_FRAGMENT)
+ goto bad_fragment;
+
KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue"));
/* Remember maximum fragment len for refragmentation. */
@@ -458,6 +464,8 @@ pf_fillup_fragment(struct pf_fragment_cmp *key, struct
TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
else
TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
+
+ frag->fr_entries++;
return (frag);
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