Date: Fri, 17 Aug 2018 15:00:10 +0000 (UTC) From: Kristof Provost <kp@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r337969 - head/sys/netpfil/pf Message-ID: <201808171500.w7HF0AU6074065@repo.freebsd.org>
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Author: kp Date: Fri Aug 17 15:00:10 2018 New Revision: 337969 URL: https://svnweb.freebsd.org/changeset/base/337969 Log: 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. MFC after: 3 days Security: CVE-2018-5391 Sponsored by: Klara Systems Modified: head/sys/netpfil/pf/pf_norm.c Modified: head/sys/netpfil/pf/pf_norm.c ============================================================================== --- head/sys/netpfil/pf/pf_norm.c Fri Aug 17 14:57:13 2018 (r337968) +++ head/sys/netpfil/pf/pf_norm.c Fri Aug 17 15:00:10 2018 (r337969) @@ -91,8 +91,10 @@ 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 */ @@ -384,6 +386,7 @@ 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); @@ -395,6 +398,9 @@ 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. */ @@ -466,6 +472,8 @@ 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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