This is a note to let you know that I've just added the patch titled
netfilter: add back stackpointer size checks
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: netfilter-add-back-stackpointer-size-checks.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 57ebd808a97d7c5b1e1afb937c2db22beba3c1f8 Mon Sep 17 00:00:00 2001
From: Florian Westphal fw@strlen.de Date: Wed, 7 Feb 2018 13:46:25 +0100 Subject: netfilter: add back stackpointer size checks
From: Florian Westphal fw@strlen.de
commit 57ebd808a97d7c5b1e1afb937c2db22beba3c1f8 upstream.
The rationale for removing the check is only correct for rulesets generated by ip(6)tables.
In iptables, a jump can only occur to a user-defined chain, i.e. because we size the stack based on number of user-defined chains we cannot exceed stack size.
However, the underlying binary format has no such restriction, and the validation step only ensures that the jump target is a valid rule start point.
IOW, its possible to build a rule blob that has no user-defined chains but does contain a jump.
If this happens, no jump stack gets allocated and crash occurs because no jumpstack was allocated.
Fixes: 7814b6ec6d0d6 ("netfilter: xtables: don't save/restore jumpstack offset") Reported-by: syzbot+e783f671527912cd9403@syzkaller.appspotmail.com Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/ipv4/netfilter/arp_tables.c | 4 ++++ net/ipv4/netfilter/ip_tables.c | 7 ++++++- net/ipv6/netfilter/ip6_tables.c | 4 ++++ 3 files changed, 14 insertions(+), 1 deletion(-)
--- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -257,6 +257,10 @@ unsigned int arpt_do_table(struct sk_buf } if (table_base + v != arpt_next_entry(e)) { + if (unlikely(stackidx >= private->stacksize)) { + verdict = NF_DROP; + break; + } jumpstack[stackidx++] = e; }
--- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -335,8 +335,13 @@ ipt_do_table(struct sk_buff *skb, continue; } if (table_base + v != ipt_next_entry(e) && - !(e->ip.flags & IPT_F_GOTO)) + !(e->ip.flags & IPT_F_GOTO)) { + if (unlikely(stackidx >= private->stacksize)) { + verdict = NF_DROP; + break; + } jumpstack[stackidx++] = e; + }
e = get_entry(table_base, v); continue; --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -357,6 +357,10 @@ ip6t_do_table(struct sk_buff *skb, } if (table_base + v != ip6t_next_entry(e) && !(e->ipv6.flags & IP6T_F_GOTO)) { + if (unlikely(stackidx >= private->stacksize)) { + verdict = NF_DROP; + break; + } jumpstack[stackidx++] = e; }
Patches currently in stable-queue which might be from fw@strlen.de are
queue-4.15/netfilter-add-back-stackpointer-size-checks.patch queue-4.15/netfilter-ipv6-fix-use-after-free-write-in-nf_nat_ipv6_manip_pkt.patch queue-4.15/netfilter-ebtables-config_compat-don-t-trust-userland-offsets.patch queue-4.15/netfilter-bridge-ebt_among-add-missing-match-size-checks.patch